Benchmark Email Lite creates a newsletter signup form widget.
Custom Category Templates allows you to define custom templates for category views.
FoxyPress is a custom plugin made to integrate FoxyCart e-commerce functionality into your WordPress website.
IntenseDebate is a feature-rich comment system for WordPress, Blogger, Tumblr and many other blogging/CMS platforms.
Jetpack supercharges your self-hosted WordPress site with the awesome cloud power of WordPress.com.
Joemobi allows you to create native Android and BlackBerry applications from your WordPress site.
Social allows you to broadcast posts to Twitter and/or Facebook, pull in items from each as comments, and allow commenters to use their Twitter/Facebook identities.
WP Super Cache is a very fast caching engine for WordPress that produces static html files.