Joomla is one of the leading open-source Content Management Systems. With a userbase of over 400,000, they use phpBB as a reliable platform for support.
Discussion forum for the massively popular American animated sitcom. Powered by phpBB.
Official Support Forum for Debian, the kernel-based open source operating system. phpBB provides a solid platform for support and discussion.
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.
Pixelmator is a popular commercial image editing software for Mac OS X users.
Gentoo Linux is an open source operating system built on top of the Linux kernel and based on the Portage package management system.