The VideoLAN project produces the extremely popular VLC media player software. Their forums provide support for users of the software as well as the development community.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.
Professional online broker and trading community.
GameServers is a premier Game Hosting company, having collaborations with big names such as Infinity Ward, Treyarch and Epic Studios.
Pixelmator is a popular commercial image editing software for Mac OS X users.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.