WordPress.org

A very fast caching engine for WordPress that produces static html files.

By: Donncha O Caoimh, Automattic, and Brandon Kraft.

BuddyPress helps site builders and WordPress developers add community features to their websites, with user profile fields, activity streams, messagin

By: John James Jacoby, Paul Gibbs, Boone Gorges, r-a-y, imath, @mercime, and others.

bbPress is forum software, made the WordPress way.

By: Matt Mullenweg, John James Jacoby, Jennifer M. Dodd, and Stephen Edgar.

Akismet checks your comments against the Akismet Web service to see if they look like spam or not.

By: Matt Mullenweg, Ryan Boren, Andy Skelton, Michael Adams (mdawaffe), and others.

Increase your traffic, view your stats, speed up your site, and protect yourself from hackers with Jetpack.

By: Automattic, Adam Heckler, Andrew Duthie, Alex Kirk, allendav, alternatekev, and others.

A simple and easy way to test your theme for all the latest WordPress standards and practices. A great theme development tool!

By: Samuel Wood (Otto) and Simon Prosser.