10 Essential Plug-ins for WordPress Version 2.1

Akismet - comment anti-spam (from Matt Mullenweg available at Akismet)
Do Follow - disables the “nofollow” tagging in comments (by Kimmo Suominen available at his website)
Meta-Tags - meta tag management for your blog (by Can Erten available here)
Optimal Title - puts the title of articles first on the title of the page (by Aaron Schaefer available on his ElasticDog blog)
Recent Comments - shows recent comments with link back to commenter’s site and link to comment (by Liew Cheon Fong and available on his blog)
Related Posts - creates a list of posts that are related to the one above (by Alexander Malov, Mike Lu & Jon Bourne and available here [Editor’s note: the wasabi website seems to be down and has been for several days]
PHP Contact Form - adds a form based contact page that is spam proof (by Mike Cherim and Mike Jolley available here)
Subscribe to Comments - notifies commenter’s via email when someone else makes a comment on the thread (by Mark Jaquith and available here)
WordPress Database Backup - on-demand and scheduled backup of your blog database (by Scott Merrill and Atin Matzko and available here)
WP-Cache - fast caching of your blog pages (by Ricardo Galli Granada and available here)