Mozmill is a test automation tool for Gecko based applications. While its primary use is automating Firefox and Thunderbird tests, it can also be used to test extensions or as a general purpose driver. Like most Mozilla projects, Mozmill is open source.
Taedium is a school project which aims to solve the common cycle of boredom ("I don't know, what do you want to do?"). Taedium will provide a stumbleupon like interface for discovering new activities nearby based on your likes and disklikes.
Firebug Test Runner
The Firebug Test Runner is a tool I made for automating the process of running the Firebug unit tests. It is currently deployed on three virtual machines inside Mozilla's network and is reporting results to Firebug's website.