"A list of hooks in all* Drupal contrib modules (6.x and 7.x), in descending order of how often they're implemented. (Consolidated a few that were renamed between 6 and 7) * Within a rounding error. :P"
https://gist.github.com/webchickenator/4409685
Reproduced below in case the link above ever breaks.
Array
(
[hook_menu] => 6744
[hook_uninstall] => 4742
[hook_perm(ission)] => 4012
[hook_install] => 3751
[hook_theme] => 3525
[hook_schema] => 3003
[hook_help] => 2465
[hook_form_alter] => 2273
[hook_views_api] => 1621
[hook_init] => 1621
[hook_block_info+hook_block] => 1341
[hook_nodeapi+hook_node_insert] => 1215
[hook_requirements] => 989
[hook_enable] => 955
[hook_cron] => 834
[hook_views_default_views] => 784
[hook_block_view] => 746
[hook_ctools_plugin_api] => 717
[hook_field_formatter_info] => 710
[hook_views_data] => 680
[hook_node_info] => 543
[hook_user+hook_user_delete] => 542
[hook_menu_alter] => 528
[hook_form] => 526
[hook_field_formatter_view] => 513
[hook_disable] => 471
[hook_field_info] => 419
[hook_drush_command] => 413
[hook_views_handlers] => 389
[hook_ctools_plugin_directory] => 344
[hook_field_widget_info] => 344
[hook_field_widget_form] => 327
[hook_node_view] => 321
[hook_views_plugins] => 313
[hook_node_update] => 300
[hook_node_delete] => 293
[hook_strongarm] => 290
[hook_rules_action_info] => 287
[hook_views_data_alter] => 280
[hook_field_is_empty] => 277
[hook_field_schema] => 273
[hook_load] => 266
[hook_block_configure] => 265
[hook_mail] => 256
[hook_theme_registry_alter] => 256
[hook_field_formatter_settings_summary] => 255
[hook_field_formatter_settings_form] => 253
[hook_update] => 250
[hook_drush_help] => 249
[hook_entity_info] => 247
[hook_field_default_fields] => 245
[hook_block_save] => 243
[hook_elements] => 225
[hook_tokens] => 224
[hook_insert] => 218
[hook_delete] => 216
[hook_rules_event_info] => 215
[hook_token_info] => 215
[hook_access] => 212
[hook_view] => 203
[hook_validate] => 202
[hook_info] => 201
[hook_entity_info_alter] => 198
[hook_filter_info] => 197
[hook_link] => 187
[hook_page_alter] => 185
[hook_token_list] => 183
[hook_token_values] => 181
[hook_user_default_permissions] => 178
[hook_node_load] => 178
[hook_action_info] => 177
[hook_widget_info] => 171
[hook_element_info] => 170
[hook_flush_caches] => 170
[hook_field_extra_fields] => 161
[hook_widget] => 157
[hook_library] => 155
[hook_rules_condition_info] => 151
[hook_field_validate] => 148
[hook_commerce_payment_method_info] => 146
[hook_forms] => 145
[hook_default_rules_configuration] => 141
[hook_boot] => 141
[hook_schema_alter] => 138
[hook_admin_paths] => 137
[hook_filter] => 132
[hook_field_widget_error] => 131
[hook_user_insert] => 127
[hook_field_widget_settings_form] => 125
[hook_preprocess_page] => 123
[hook_field_settings_form] => 122
[hook_field_settings] => 121
[hook_widget_settings] => 120
[hook_filter_tips] => 119
[hook_features_export] => 118
[hook_field] => 117
[hook_content_is_empty] => 115
[hook_context_default_contexts] => 115
[hook_features_export_options] => 114
[hook_payment_method] => 114
[hook_features_revert] => 113
[hook_form_submit] => 112
[hook_features_export_render] => 110
[hook_module_implements_alter] => 109
[hook_exit] => 109
[hook_features_api] => 107
[hook_submit] => 107
[hook_settings] => 106
[hook_user_login] => 100
[hook_user_view] => 100
[hook_user_update] => 100
[hook_menu_local_tasks_alter] => 99
[hook_context_plugins] => 98
[hook_user_presave] => 96
[hook_field_instance_settings_form] => 96
[hook_update_last_removed] => 95
[hook_context_registry] => 94
[hook_node_access] => 93
[hook_content_default_fields] => 93
[hook_image_default_styles] => 93
[hook_modules_enabled] => 92
[hook_ctools_plugin_type] => 91
[hook_node_presave] => 91
[hook_comment] => 90
[hook_field_presave] => 87
[hook_entity_delete] => 86
[hook_user_cancel] => 86
[hook_page_build] => 81
[hook_entity_insert] => 80
[hook_element_info_alter] => 80
[hook_node_type] => 79
[hook_entity_property_info_alter] => 77
[hook_node_access_records] => 77
[hook_features_rebuild] => 76
[hook_libraries_info] => 75
[hook_taxonomy] => 75
[hook_cron_queue_info] => 74
[hook_taxonomy_default_vocabularies] => 73
[hook_node_grants] => 73
[hook_file_download] => 71
[hook_order] => 70
[hook_user_load] => 69
[hook_wysiwyg_plugin] => 68
[hook_footer] => 68
[hook_entity_update] => 65
[hook_views_pre_render] => 65
[hook_feeds_plugins] => 64
[hook_admin_settings] => 64
[hook_form_validate] => 64
[hook_variable_info] => 63
[hook_mail_alter] => 63
[hook_comment_insert] => 62
[hook_node_validate] => 61
[hook_content_extra_fields] => 59
[hook_field_widget_info_alter] => 59
[hook_link_alter] => 59
[hook_xmlrpc] => 57
[hook_rules_data_info] => 57
[hook_field_access] => 57
[hook_node_type_delete] => 56
[hook_entity_property_info] => 55
[hook_node_prepare] => 55
[hook_user_logout] => 55
[hook_field_load] => 54
[hook_preprocess_node] => 53
[hook_taxonomy_term_delete] => 53
[hook_field_attach_form] => 52
[hook_services_resources] => 52
[hook_node_operations] => 50
[hook_field_update] => 49
[hook_stream_wrappers] => 49
[hook_service] => 49
[hook_node_type_update] => 49
[hook_comment_update] => 48
[hook_system_info_alter] => 46
[hook_uc_payment_method] => 45
[hook_watchdog] => 45
[hook_ca_predicate] => 45
[hook_user_default_roles] => 45
[hook_migrate_api] => 44
[hook_modules_disabled] => 44
[hook_node_view_alter] => 44
[hook_field_insert] => 44
[hook_comment_view] => 43
[hook_custom_theme] => 43
[hook_node_revision_delete] => 43
[hook_comment_delete] => 43
[hook_flag_default_flags] => 43
[hook_field_group_info] => 43
[hook_menu_link_alter] => 43
[hook_feeds_importer_default] => 43
[hook_file_delete] => 42
[hook_feeds_processor_targets_alter] => 42
[hook_field_views_data] => 42
[hook_url_outbound_alter] => 42
[hook_update_index] => 41
[hook_preprocess_html] => 41
[hook_field_attach_view_alter] => 41
[hook_search] => 40
[hook_taxonomy_term_insert] => 40
[hook_entity_load] => 40
[hook_ca_action] => 40
[hook_field_formatter_prepare_view] => 40
[hook_menu_default_menu_links] => 39
[hook_webform_component_info] => 38
[hook_field_widget_form_alter] => 38
[hook_field_prepare_view] => 38
[hook_js_alter] => 38
[hook_default_page_manager_pages] => 38
[hook_update_dependencies] => 38
[hook_imagecache_default_presets] => 37
[hook_preprocess] => 37
[hook_entity_view] => 37
[hook_taxonomy_term_update] => 37
[hook_views_query_alter] => 36
[hook_default_page_manager_handlers] => 36
[hook_field_info_alter] => 36
[hook_entity_presave] => 36
[hook_node_import_fields] => 36
[hook_file_formatter_info] => 35
[hook_options_list] => 35
[hook_file_default_displays] => 34
[hook_taxonomy_vocabulary_delete] => 34
[hook_user_operations] => 33
[hook_search_execute] => 33
[hook_views_default_views_alter] => 32
[hook_variable_group_info] => 32
[hook_checkout_pane] => 32
[hook_block_view_alter] => 32
[hook_search_info] => 32
[hook_payment_gateway] => 32
[hook_value] => 31
[hook_trigger_info] => 31
[hook_contextual_links_view_alter] => 30
[hook_field_delete_instance] => 30
[hook_autoload_info] => 30
[hook_commerce_checkout_pane_info] => 30
[hook_wysiwyg_include_directory] => 30
[hook_field_delete] => 29
[hook_user_categories] => 29
[hook_pathauto] => 29
[hook_token_info_alter] => 29
[hook_field_formatter_info_alter] => 29
[hook_context_page_reaction] => 28
[hook_permissions] => 28
[hook_media_internet_providers] => 27
[hook_views_plugin] => 27
[hook_uc_order] => 27
[hook_modules_uninstalled] => 26
[hook_rdf_namespaces] => 26
[hook_db_rewrite_sql] => 26
[hook_modules_installed] => 26
[hook_css_alter] => 26
[hook_admin] => 26
[hook_translated_menu_link_alter] => 25
[hook_simpletest] => 25
[hook_preprocess_block] => 25
[hook_default_view_views] => 25
[hook_og_permission] => 24
[hook_ca_trigger] => 24
[hook_rules_file_info] => 24
[hook_selector_map] => 24
[hook_ucga_display] => 24
[hook_alter] => 24
[hook_def] => 23
[hook_apps_app_info] => 23
[hook_locale] => 23
[hook_url_inbound_alter] => 22
[hook_content_migrate_instance_alter] => 22
[hook_block_list_alter] => 22
[hook_hose_xml_field_name] => 22
[hook_filter_default_formats] => 22
[hook_themekey_properties] => 22
[hook_comment_publish] => 22
[hook_hose_xml_field_icon] => 22
[hook_hose_xml_validate] => 22
[hook_rules_data_type_info] => 22
[hook_order_pane] => 22
[hook_widget_settings_alter] => 22
[hook_hose_xml_settings_information] => 22
[hook_preprocess_hook] => 22
[hook_notifications] => 22
[hook_media_parse] => 22
[hook_entity_view_alter] => 21
[hook_taxonomy_vocabulary_update] => 21
[hook_field_update_instance] => 21
[hook_library_alter] => 21
[hook_search_access] => 21
[hook_flag] => 21
[hook_views_pre_view] => 21
[hook_field_create_instance] => 21
[hook_content_migrate_field_alter] => 21
[hook_node_type_insert] => 21
[hook_html_head_alter] => 20
[hook_recurring_info] => 20
[hook_date_format_types] => 20
[hook_apps_compatible_info] => 20
[hook_preprocess_author_pane] => 20
[hook_menu_link_update] => 20
[hook_default_services_endpoint] => 20
[hook_prepare] => 20
[hook_db_def_tables] => 19
[hook_allowed_values] => 19
[hook_image_effect_info] => 19
[hook_lt_themable] => 19
[hook_action_info_alter] => 19
[hook_captcha] => 19
[hook_context_page_condition] => 19
[hook_registry_files_alter] => 19
[hook_reviews] => 19
[hook_date_formats] => 19
[hook_node_access_explain] => 19
[hook_webform_submission_insert] => 19
[hook_field_delete_revision] => 19
[hook_views_post_render] => 18
[hook_menu_default_menu_custom] => 18
[hook_admin_menu_map] => 18
[hook_views_pre_execute] => 18
[hook_comment_presave] => 18
[hook_userpoints] => 18
[hook_search_reset] => 18
[hook_ca_condition] => 18
[hook_node_import_defaults] => 18
[hook_update_n] => 18
[hook_line_item] => 17
[hook_query_alter] => 17
[hook_search_status] => 17
[hook_admin_paths_alter] => 17
[hook_content_build_modes] => 17
[hook_menu_link_delete] => 17
[hook_mollom_form_info] => 17
[hook_tokens_alter] => 17
[hook_field_attach_submit] => 17
[hook_comment_unpublish] => 17
[hook_add_to_cart] => 17
[hook_cart_item] => 17
[hook_node_submit] => 17
[hook_taxonomy_vocabulary_insert] => 17
[hook_node_update_index] => 16
[hook_commerce_line_item_type_info] => 16
[hook_service_links] => 16
[hook_uc_store_status] => 16
[hook_bean_types] => 16
[hook_entity_uuid_load] => 16
[hook_bean_types_api_info] => 16
[hook_commerce_tax_rate_info] => 16
[hook_voipscript_get_script_names] => 16
[hook_feedapi_settings_form] => 16
[hook_entity_uuid_presave] => 16
[hook_node_import_values_alter] => 16
[hook_block_list] => 16
[hook_mollom_form_list] => 16
[hook_menu_link_insert] => 16
[hook_faceted_search_collect] => 16
[hook_gateway_info] => 16
[hook_ds_fields] => 16
[hook_user_role_delete] => 16
[hook_comment_view_alter] => 16
[hook_views_pre_build] => 15
[hook_image] => 15
[hook_file_mimetype_mapping_alter] => 15
[hook_profile_alter] => 15
[hook_comment_load] => 15
[hook_clone_node_alter] => 15
[hook_uc_checkout_complete] => 15
[hook_swftools_methods] => 15
[hook_search_api_service_info] => 15
[hook_file_insert] => 15
[hook_field_formatter_settings_summary_alter] => 15
[hook_views_bulk_operations_object_info] => 15
[hook_foo] => 15
[hook_messaging] => 15
[hook_facetapi_widgets] => 15
[hook_user_view_alter] => 14
[hook_field_formatter_settings_form_alter] => 14
[hook_entity_query_alter] => 14
[hook_commerce_shipping_method_info] => 14
[hook_commerce_shipping_service_info] => 14
[hook_styles_default_presets] => 14
[hook_field_attach_delete_bundle] => 14
[hook_uc_payment_gateway] => 14
[hook_commerce_order_status_info] => 14
[hook_course_handlers] => 14
[hook_styles_default_containers] => 14
[hook_media_mover] => 14
[hook_facetapi_facet_info] => 14
[hook_uc_message] => 14
[hook_field_attach_rename_bundle] => 14
[hook_panels_pane_content_alter] => 14
[hook_drush_init] => 14
[hook_admin_menu_output_alter] => 14
[hook_defaultconfig_field_default_fields] => 14
[hook_views_tables] => 14
[hook_process_html] => 14
[hook_file_update] => 13
[hook_field_attach_presave] => 13
[hook_path_alias_types] => 13
[hook_create_content] => 13
[hook_menu_delete] => 13
[hook_field_formatter] => 13
[hook_ctools_plugin_dierctory] => 13
[hook_ca_entity] => 13
[hook_search_admin] => 13
[hook_receipt_info] => 13
[hook_views_plugins_alter] => 13
[hook_feeds_tamper_default] => 13
[hook_page_title_pattern_alter] => 13
[hook_voipscript_load_script] => 13
[hook_node_link_style] => 13
[hook_context_links_alter] => 13
[hook_uc_shipping_method] => 13
[hook_form_user_profile_form_alter] => 13
[hook_openlayers_layers] => 13
[hook_preprocess_comment] => 13
[hook_rdf_mapping] => 13
[hook_views_query_substitutions] => 13
[hook_file_validate] => 13
[hook_quiz_question_info] => 13
[hook_preprocess_views_view] => 12
[hook_activity_info] => 12
[hook_product_feature] => 12
[hook_block_info_alter] => 12
[hook_date_api_fields] => 12
[hook_field_extra_fields_alter] => 12
[hook_apachesolr_update_index] => 12
[hook_styles_register] => 12
[hook_wysiwyg_default_profiles] => 12
[hook_ckeditor_plugin] => 12
[hook_feature_info] => 12
[hook_features_pipe_alter] => 12
[hook_media_format_form_prepare_alter] => 12
[hook_subscriptions] => 12
[hook_field_attach_update] => 12
[hook_file_download_access] => 12
[hook_search_preprocess] => 12
[hook_panelizer_defaults] => 12
[hook_styles_presets] => 12
[hook_menu_contextual_links_alter] => 12
[hook_defaults] => 12
[hook_file_load] => 12
[hook_redirect_form_validate] => 12
[hook_fieldgroup_default_groups] => 12
[hook_views_style_plugins] => 12
[hook_boxes_plugins] => 12
[hook_default_value] => 12
[hook_wysiwyg_editor_settings_alter] => 12
[hook_webform_submission_update] => 12
[hook_page_delivery_callback_alter] => 12
[hook_menu_site_status_alter] => 12
[hook_field_attach_insert] => 12
[hook_node_widget_widgets_info] => 12
[hook_cronapi] => 12
[hook_facebook_status_delete] => 12
[hook_feeds_node_processor_targets_alter] => 12
[hook_apachesolr_field_mappings] => 12
[hook_features_export_alter] => 11
[hook_ds_fields_info] => 11
[hook_domain_delete] => 11
[hook_locationapi] => 11
[hook_devel_generate] => 11
[hook_name] => 11
[hook_emfield_providers] => 11
[hook_commerce_order_state_info] => 11
[hook_view_api] => 11
[hook_page_title_settings] => 11
[hook_author_pane_allow_preprocess_disable] => 11
[hook_content_defaults] => 11
[hook_activity_grants] => 11
[hook_default_panels_mini] => 11
[hook_page_title_alter] => 11
[hook_flag_definitions] => 11
[hook_purl_provider] => 11
[hook_default_search_api_index] => 11
[hook_field_update_field] => 11
[hook_apachesolr_modify_query] => 11
[hook_taxonomy_term_presave] => 11
[hook_drupal_goto_alter] => 11
[hook_entity_prepare_view] => 11
[hook_media_browser_plugin_info] => 11
[hook_crumbs_plugins] => 11
[hook_apachesolr_query_alter] => 11
[hook_date_api_tables] => 11
[hook_rules_defaults] => 11
[hook_language_negotiation_info] => 11
[hook_field_storage_pre_insert] => 11
[hook_field_storage_pre_update] => 11
[hook_filefield_sources_info] => 11
[hook_menu_get_item_alter] => 11
[hook_openlayers_maps] => 10
[hook_checkout_info] => 10
[hook_search_page] => 10
[hook_statuses_delete] => 10
[hook_field_delete_field] => 10
[hook_default_message_type] => 10
[hook_styles_styles] => 10
[hook_field_settings_alter] => 10
[hook_features_export_rebuild] => 10
[hook_image_style_delete] => 10
[hook_userpoints_info] => 10
[hook_variable_type_info] => 10
[hook_perms] => 10
[hook_content_fieldapi] => 10
[hook_dqx_adminmenu_items] => 10
[hook_themekey_paths] => 10
[hook_form_form_id_alter] => 10
[hook_user_import_after_save] => 10
[hook_views_slideshow_option_definition] => 10
[hook_activity_access_grants] => 10
[hook_views_post_execute] => 10
[hook_jq] => 10
[hook_ctools_render_alter] => 10
[hook_uc_checkout_pane] => 10
[hook_file_styles_filter] => 10
[hook_store_status] => 10
[hook_openid] => 10
[hook_menu_breadcrumb_alter] => 10
[hook_styles_containers] => 10
[hook_term_path] => 10
[hook_field_attach_load] => 10
[hook_preprocess_field] => 10
[hook_default_box] => 10
[hook_dependent_fields_widget_form] => 10
[hook_domainupdate] => 10
[hook_spaces_plugins] => 10
[hook_nodewords_type_id] => 10
[hook_simple_contest] => 10
[hook_form_node_type_form_alter] => 10
[hook_field_views_data_views_data_alter] => 10
[hook_og_ui_get_group_admin] => 10
[hook_uc_order_pane] => 9
[hook_insert_styles] => 9
[hook_username_alter] => 9
[hook_field_attach_validate] => 9
[hook_feedapi_item] => 9
[hook_field_attach_create_bundle] => 9
[hook_defaultconfig_user_default_permissions] => 9
[hook_dqx_adminmenu_items_alter] => 9
[hook_insert_content] => 9
[hook_menu_insert] => 9
[hook_salsa_object_type_info] => 9
[hook_add_to_cart_data] => 9
[hook_form_system_theme_settings_alter] => 9
[hook_form_builder_types] => 9
[hook_openlayers_behaviors] => 9
[hook_update_status_alter] => 9
[hook_feedapi_feed] => 9
[hook_checkout_init] => 9
[hook_workflow] => 9
[hook_field_storage_delete_instance] => 9
[hook_field_storage_query] => 9
[hook_uc_product_feature] => 9
[hook_styleguide] => 9
[hook_field_create_field] => 9
[hook_backup_migrate_destination_types] => 9
[hook_field_storage_delete] => 9
[hook_trigger_name] => 9
[hook_filter_format_update] => 9
[hook_cart_pane] => 9
[hook_scald_prerender] => 9
[hook_facetapi_default_facet_settings] => 9
[hook_js] => 9
[hook_votingapi_insert] => 9
[hook_commerce_checkout_page_info] => 9
[hook_panels_dashboard_blocks] => 9
[hook_field_storage_info] => 9
[hook_fb] => 9
[hook_og_context_negotiation_info] => 9
[hook_mime_types] => 9
[hook_ucount_reports_info] => 9
[hook_nodequeue_info] => 9
[hook_defaultconfig_optionals] => 9
[hook_commerce_price_component_type_info] => 9
[hook_field_group_pre_render] => 8
[hook_views_rss_namespaces] => 8
[hook_hap_info] => 8
[hook_skinr_skin_info] => 8
[hook_field_group_format_settings] => 8
[hook_ds_layout_settings_info] => 8
[hook_field_group_formatter_info] => 8
[hook_file_presave] => 8
[hook_node_access_records_alter] => 8
[hook_field_default_field_instances] => 8
[hook_mailsave_clean] => 8
[hook_config] => 8
[hook_filter_format_disable] => 8
[hook_field_storage_load] => 8
[hook_field_uuid_presave] => 8
[hook_ajax_render_alter] => 8
[hook_fbss_comments_delete] => 8
[hook_content_migrate_data_record_alter] => 8
[hook_image_style_save] => 8
[hook_preprocess_views_view_table] => 8
[hook_field_storage_delete_revision] => 8
[hook_multilingual_settings_changed] => 8
[hook_field_storage_write] => 8
[hook_field_storage_details] => 8
[hook_field_storage_delete_field] => 8
[hook_field_storage_update_field] => 8
[hook_field_storage_create_field] => 8
[hook_overlay_parent_initialize] => 8
[hook_ctools_content_types] => 8
[hook_image_style_flush] => 8
[hook_field_update_forbid] => 8
[hook_variable_realm_info] => 8
[hook_receipt_payment_form] => 8
[hook_language_switch_links_alter] => 8
[hook_fontyourface_info] => 8
[hook_update_x] => 8
[hook_plugin_info] => 8
[hook_uc_shipping_type] => 8
[hook_dashboard_requirements] => 8
[hook_field_views_data_alter] => 8
[hook_mime_converters] => 8
[hook_filefield_source_settings] => 8
[hook_commerce_product_type_info] => 8
[hook_filefield_source_info