Prepopulate an entity reference field based off of values in the URI (http://mysite.com/node/add/article?field_my_entity_ref=134)

Take control of your breadcrumbs!

This will tame the permissions page if it is getting long (like what happens when you use content permissions and have lots of different content types.)

This shows you all the different themeable elements and lets you see how your theme renders them.

Integrate Google Maps with Drupal.

Combine maps from different sources - integrates with Views and can do a ton of map related shtuff.

A nice admin interface for managing books.

Creates calendars - integrates with Views. If you need a calendar and don't know this module, try it :)

"This module allows you to attach tabular data to a node in Drupal 6 or any entity in Drupal 7." Data can be exported to CSV (D7).