The list apparently got blown away, so I'm adding ones I can think of. Feel free to expand, it's a wiki after all!

• KDE [http://www.kde.org/]
• WINE [http://www.winehq.com/]
• Catalyst [http://dev.catalystframework.org/]
• RT [http://www.bestpractical.com/rt/]
• Jifty [http://jifty.org]
• Ruby on Rails [http://www.rubyonrails.org]
• SVK