Interesting Drupal Modules et al.
For Drupal development and administration:
coder module: Checks code against rules (coding standards, basic security checks)
devel module: Debug functions for developers
admin_menu module: Menu for drupal administrators
schema module: Extends the functionality around the schema API of Drupal 6
scaffolding_example: Helps getting started with writing a custom module
Various code examples:
http://cvs.drupal.org/viewvc.py/drupal/contributions/docs/developer/exam...
More modules:
Übercart: Shop plugin
Pathauto: Automatic creation of URL aliases for nodes
Drush: Drupal Shell, command line interface for Drupal
Panels
Views
Token
ImageField
ImageCache
Global Redirect: Send redirect from node/nid to alias URL
Meta Tags: Lets you specify meta tags for nodes, e.g. description and keywords
XML Sitemap
Trackback: Send and receive trackbacks
Tagadelic: A Tag cloud for the taxonomy terms