Gentoo Linux is an open source operating system built on top of the Linux kernel and based on the Portage package management system.
Professional online broker and trading community.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.
Discussion board for the massively popular xkcd web comic. Covering everything from Maths and Science to Logic Puzzles and Forum Games. Over 100k members and 2.4 Million posts.
GameServers is a premier Game Hosting company, having collaborations with big names such as Infinity Ward, Treyarch and Epic Studios.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.