Drupal 7

Searched for "ampersand breaks imagecache" and ultimately found this module. An & (and probably other special characters) makes a perfectly valid uploaded file but does not show up in that file's imagecache manipulations.

Provides a central transliteration service to other Drupal modules, and sanitizes file names while uploading.

Noggin module allows you to upload a custom header image on the Theme Settings page, just as you can logos and favorite icons. With Bartik and other core Drupal themes, the header image will appear automatically. For themes that use slightly different markup, you can enter in a custom CSS selector for the header region.

This is an excellent module to use as an example for Drupal's core extendability (a module modifying a theme! --even if simply by adding CSS.)

AJAX Poll adds the ability for users to vote on polls without reloading the page. It works with the normal Poll module included with Drupal core. It affects all polls throughout the site, on teaser, full, and block forms of polls.

took the time to go through a lot of issues on drupal.org, to take a large step back, and to recall the entire awesomeness we added to Drupal 7.

bootstrap.inc (2,700 lines) includes functions that are available on EVERY Drupal request.

This author starts to go through the Drupal code base a little like we envision for Definitive Drupal's Inside Drupal chapter.

But only gets as far as bootstrap.inc so far!