In-development rewrite of the WordPress (WXR) Importer
InstantWP is a complete standalone, portable WordPress development environment.
A WordPress framework that facilitates the development of WP themes
Free WordPress plugin
A collection of abstract classes, interfaces, and traits to promote object-oriented programming practices in WordPress.
WordPress plug-in, Event Organiser, development repository
Official Creative Commons plugin for licensing your content. With Creative Commons licenses, keep your copyright AND share your creativity.
A progressive theme development rig for WordPress.
No longer under active development. Moved to Warkior's fork.