My favourite Drush modules
Drush is a powerfull and must have tools for every Drupal developer. In additions to core Drush commands there are few great modules.
Here is a list of my favourites:
Module Builder
http://drupal.org/project/module_builder
A module which auto-generates a skeleton or "scaffolding" for a module, along with hints on how to fill them in. Useful for newbie developers to learn how hooks work, and seasoned developers who are too lazy to look up what arguments a function has to take. ;)
Drush Role
http://drupal.org/project/drush_role
Provides drush commands to manage roles and permissions.
Drush Language
http://drupal.org/project/drush_language
Drush commands allowing languages to be added, switched, enabled and disabled from the commandline.
You can install Drush modules by putting module in ~/.drush directory.