Hugely popular Mozilla community providing support for Firefox, Thunderbird, Seamonkey and other well known Mozilla products. Over 350k members and 4 Million posts.
Zend Technologies is one of the largest and most popular companies producing a wide variety of tools and frameworks for PHP. Their community forums rely on phpBB.
Gentoo Linux is an open source operating system built on top of the Linux kernel and based on the Portage package management system.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.
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.
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.