Shuttle - The Shuttle Project is one that involves the beautification of the WordPress administration panel.

Rin and Manji - Single and two column themes for Wordpress. These are out of date and have not been updated since version 2.0. These are however still being used in various places on the net.

FOFRedux - FOFRedux is an online RSS aggregator that sits on your server (so all your information is kept private and can be accessed from anywhere with just a web browser).

Habari - Is an open source blogging tool. Contributions made to the overall admin design and other elements.