KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
A very active community for a KFAN-AM, a popular sports radio station in Minneapolis/St. Paul, MN.
Pixelmator is a popular commercial image editing software for Mac OS X users.
Active community for UK based Audi TT owners. Almost 30k members and 2 million posts, complete with unique style & powered by phpBB.
Boasting almost 14 million posts, Ars Technica is one of the biggest and oldest technical forums still operating today. They use phpBB to power their forums and comment system.
GameServers is a premier Game Hosting company, having collaborations with big names such as Infinity Ward, Treyarch and Epic Studios.