"This module defines the "hierarchical_select" form element, which is a greatly enhanced way for letting the user select items in a hierarchy."

"Define dependencies between fields based on their states and values. "

Use PHP to create computed fields. If you use this, export the configuration so you don't have PHP in the db!

"auto_nodetitle" is a small and efficient module that allows hiding of the content title field in the form. To prevent empty content title fields one can configure it to generate the title by a given pattern.

When the token module is installed it's possible to use various node data for the
auto generated title - e.g. use the text of a CCK field (since 5.x).

Advanced

Combines autocomplete with a 'select or other' type of dropdown. The best / closest thing to select or other that I've found which works for taxonomy terms.

Let's you arrange the fields in a form to be displayed in a custom layout. Check out this image:

"The Field Permissions module allows site administrators to set field-level permissions to edit, view and create fields on any entity."

Inline editing for fields. Still an alpha module at the time of this writing but I've used it and it works :) One handy thing you can do is create a view that has editable fields to get custom streamlined editing interfaces.

The de facto date field for Drupal.

"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).