WereWP

Can themes style the visual editor? « Andrew Ozz on WordPress
A great way to replicate the styling of your blog right into your visual editor. Really helpful while writing! See an example in images on the 2010 development blog

Welcome CollabPress: Project and Task Management for WordPress and WPMU – WordPress MU and BuddyPress plugins, themes, [...]

For all beginners with WordPress, and sometimes even for pros, a bit of help is needed when looking for a code snippet or a special WordPress function. Of course, Codex is here for that, and there are plenty of great tutorials on the Internet, but sometimes it is not enough: the information can be hard [...]

Geeky bits in WordPress 2.9 – Yoast
A list of all upcoming interesting features of WordPress 2.9 for developers and users.

Web Design WordPress function list
A nice ordered list about WordPress functions. It can be helpful in parallel with the codex.

20+ Brand New and Incredibly Useful WordPress Plugins – Nettuts+
A list of 21 Useful WordPress Plugins, from styling to security.