KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
Info-Mac is a community dating back to 1984 as a mailing list and was the first online community for Apple's Macintosh computer. All of their content was converted to phpBB in 2007.
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.
Hugely popular Mozilla community providing support for Firefox, Thunderbird, Seamonkey and other well known Mozilla products. Over 350k members and 4 Million posts.
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.
Boasting almost 14 million posts, Ars Technica is one of the biggest and oldest technical forums still operating today. They use phpBB to power their forums and comment system.