Category Posts Widget displays the most recent posts from a specific category.
Easy Gravatars makes it simple to add Gravatars to your blog.
Hiddy is a captcha-like plugin to help fight spam comments.
Highlight Author Comments automatically displays comments made by a post’s author in a distinctive style with no need to edit your template files.
Random Categories with Random Posts picks random entries from random categories to display on your blog. (For WordPress 2.2.3 and lower.)
Sensitive Tag Cloud provides a tagcloud that shows tags depending of the current context only.