I recently stumbled upon Ohloh and thought of letting you all know about it. As given on the site “Ohloh is a free public directory of open source software and people. Ohloh is a wiki, and anyone is welcome to join our community and add new projects to our directory, or to make corrections to existing directory pages. This public review makes Ohloh one of the largest, most accurate, and up-to-date software directories available.”
You can see a list of open source software over here
Out of the many more open source software directories out there, two worth mentioning are sourceforge and freshmeat. Microsoft’s own CodePlex is an open source project hosting web site and is pretty cool!