Wikipedia
Mozdev.org
mozdev.org is a website that offers free project hosting, and software development tools to the Mozilla community. Many Firefox extensions are hosted on the site, but Thunderbird and SeaMonkey extensions and stand-alone Mozilla-based applications can also be found. It is free to set up a project there, but all development must be done using a license approved by the OSI. Over 250 projects are currently under active development on Mozdev.