Hugely popular Mozilla community providing support for Firefox, Thunderbird, Seamonkey and other well known Mozilla products. Over 350k members and 4 Million posts.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.
VirtualBox, developed by Oracle, is cross-platform x86 virtualisation software. It has become one of the most widely used virtualisation solutions in the world.
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.
Pixelmator is a popular commercial image editing software for Mac OS X users.