This PHP snippet will list all enabled themes and modules in a colophon page. You can change the first two variables to change what is displayed.
The field_extract module provides a couple of easy-to-use functions that make extracting data from entity fields much easier - as a developer you don't have to worry about languages and deltas, you just make the call.
Displays system messages in fully themeable colored horizontal bars on top of the page, similar to Stack Overflow / Stack Exchange network notifications.
The Asset module proposes a new approach to the media management in Drupal, resolving a long-standing problem of reusable media files (images, videos, documents, etc) that evolved into the problem of reusable media content (images/videos/documents/etc with the attached content like description/licence/etc).
The Authcache module offers page caching for both anonymous users and logged-in authenticated users. This allows Drupal/PHP to only spend 1-2 milliseconds serving pages, greatly reducing server resources.
This module adds a tab to the content types page which lets you edit the settings for all content types on one screen. This makes it much easier to ensure consistent settings across content types.