drupal-6--02-most-useful-modules
It's not surprising that my list is similar to drupal's most downloaded list.
http://drupal.org/project/modules
admin = vastly improves the ability to configure drupal
cck = allows custom fields to be added to content types
token = allows variables such as /%%user/ , extremely useful with cck
pathauto = automatically renames content from node/136 to "title-of-content"
views = allows sorting of content - very powerful!
tagadelic = creates a "cloud" of most used tags (very interesting as a block)
filefield = universal upload module with size
imagefield = better management of image file uploads
imageapi
imagecache
wysiwyg
google analytics module
xml sitemap
lightbox2?
video?
advanced_help = allows tutorials and specific help for modules
captcha = prevent spammers from comments or trying to brute force logins
mollom = module to block spam (99.93%) by Dries Buytaert founder of Drupal
transliteration = multiple character sets (e.g. cyrillic)
i18n = translation of content and menus
translation_management = simple centralized management of translations
fckedito & imce?
better_formats = allows a default input format for each role