KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
Inspired by Max Berry's book, Jennifer Government, NationStates is one of the most popular online simulation games. The forum boasts over 5 million posts and 200,000 users.
As the official board for the world-famous band Queen, this community hosts a wide variety of discussions by Queen fans from around the globe.
Gentoo Linux is an open source operating system built on top of the Linux kernel and based on the Portage package management system.
Avant Browser is a fast and user friendly browser which uses Microsoft's Trident rendering engine. The browser has been downloaded over 22 million times.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.