My Most frequently used module list is below :-)
Image Modules:-
http://drupal.org/project/image
http://drupal.org/project/imageapi
http://drupal.org/project/imagecache
HTML Mailing:-
http://drupal.org/project/mimemail
Admin Functions:-
http://drupal.org/project/admin_menu
Site Navigations:-
http://drupal.org/project/nice_menus
Editing Page With HTML :-
http://drupal.org/project/wysiwyg
http://drupal.org/project/ckeditor
CCK Helpers:-
Video Audio And image files:-
http://drupal.org/project/filefield
http://drupal.org/project/imagefield
http://drupal.org/project/emfield
User Profile , registerations:-
http://drupal.org/project/content_profile
Ratings, Votings:-
http://drupal.org/project/votingapi
http://drupal.org/project/fivestar
E-Commerce:-
http://drupal.org/project/ubercart
User & SEO Helper modules:
http://drupal.org/project/token
http://drupal.org/project/pathauto
http://drupal.org/project/views
http://drupal.org/project/cck
Ajax And Inline Editing Of Fields In Drupal:-
http://www.appelsiini.net/projects/jeditable
http://drupal.org/project/edit_section
http://drupal.org/project/editview
http://drupal.org/project/editview
http://drupal.org/project/editablefields
http://drupal.org/project/tag_editor
http://www.nicklewis.org/40-essential-drupal-6-modules
http://drupal.org/project/usage
http://drupal.org/project/cck_teaser_field
http://drupal.org/project/comment_upload