I have 2 sites in Drupal, here’s my recommendations.

1. CCK http://drupal.org/project/cck The Content Construction Kit allows you create and customize fields using a web browser.

2. Flickr http://drupal.org/project/flickr allows a block to put your latest photos from flickr on there or photos with certain tags

3. Adsense injector http://drupal.org/project/adsense_injector - puts adsense ads on your site (requires Adsense http://drupal.org/project/adsense module)

4. Diggthis http://drupal.org/project/diggthis Displays a Digg this button in nodes of enabled types. See http://digg.com/tools/integrate

5. Dynamic Logo http://drupal.org/project/dynamic_logo Enables you to add more than one logo that display on specific calendar events.

6. Depends on: Image http://drupal.org/project/image

7. IE Destroyer http://drupal.org/project/iedestroyer Displays a banner ad at the top of your site to promote Firefox when IE users visit your page.

8. OpenID http://drupal.org/project/openid Allows Drupal to act as an OpenID relying party.

9. Printer-friendly pages http://drupal.org/project/print Adds a printer-friendly version link to node pages.

10. Safari Search http://drupal.org/node/100466 Replaces the search field with a input of type “search” in Safari.

11. Trackback http://drupal.org/project/trackback Allow for sending and receiving TrackBacks, which is a way for sites to notify another that they have commented on a post. Remember to turn moderation on!

12. Twitter http://drupal.org/project/twitter This module posts blog updates to twitter.com

13. Feedburner http://drupal.org/project/feedburner Integrates with FeedBurner services, primarily feed redirection.

14. User Karma http://drupal.org/project/user_karma Takes into account a user’s karma

15. Depends on: Voting API (http://drupal.org/project/votingapi)

16. Drigg http://drupal.org/project/drigg Provides a digg-like site voting system (needs voting api http://drupal.org/project/votingapi)

17. Custom Links http://drupal.org/project/custom_links Allows administrators to add custom links to nodes. More By This Author, Visit Bob’s Blog, etc.

18. Akismet http://drupal.org/project/akismet Use the Akismet Service to protect your site from spam.

19. Import Export API http://drupal.org/project/importexportapi Allows data entities in Drupal to be imported and exported in a variety of formats.

20. Backup http://drupal.org/project/backup Backup your site to a tarball

21. XML Sitemap http://drupal.org/project/xmlsitemap Creates an XML site map in accordance with the sitemaps.org specification.

22. YUI http://drupal.org/project/yui The Yahoo! User Interface Library Rich text editor, Menu, and Calendar

23. widgEditor http://drupal.org/project/widgeditor widgEditor is an easily installed, easily customisable WYSIWYG editor for simple content.

24. TinyMCE http://drupal.org/project/tinymce another popular WYSIWYG editor

25. Yahoo! Browser-Based Authentication http://drupal.org/project/yahoo_bbauth allows logins using Yahoo! Browser-Based authentication.

26. BONUS! Here’s a thread on drupal forums tell their top 10 http://drupal.org/node/155918