Must have Drupal modules. These modules easily extend the usability of Drupal to the insane. Some are handy timesavers, some are insanely powerful... 

• CCK (Content Construction Kit)
  Allows you to add custom fields to content types. Depends on sub-modules for advanced functionality.
  • Computed Field (use PHP to generate a field)
  • Link (URL field)
  • Option Widgets (selectbox, radio buttons, check box)
• Date (modules for date/time)
• Image (Image helpers)
  • Image Assist (makes including images into content easier. Butt-ugly tho)
  • Image Gallery (taxonomy based galleries. Unwieldy)
• Akismet (Heuristic-based centralised spam filter service) (Also, maybe try Mollom, by Dries himself)
• Comment closer (close comments after x time. Cuts back on invisible spam)
• DHTML menu (menu's are now ajaxy and sexy)
• Pathauto (automatically make URL aliases based on token replacement)
• Poormanscron (for people too lazy to set up (ana)cron)
• Submitted by (minimod for .submitted themeing)
• Synonym collapsing (synonyms == base term)
• Tag tool (makes choosing tags easier)
• Taxonomy manager (AJAX admin interface to organise big tag clouds)
• Wysiwyg (allows you to install various WYSIWYG editors)
• Token (allows you to tokenise other modules. Dependency)
• Token actions (allows actions to be tokenised)
• Tagadelic (makes tag clouds, accepts URL arguments)
• Views (powerful tool for custom lists and more. Must-have)
• Fivestar (rating module)
• Voting API (rating API)
• Activitystream (will import events from Flickr, last.fm, or other services (by submodule))
• ed_readmore (tweak the read_more link)
• submitted_by (tweak the submitted by information)