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.
OpenCart is popular, powerful, and easy to use shopping cart software. Their healthy community forums are powered by phpBB.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.
Professional online broker and trading community.
Pixelmator is a popular commercial image editing software for Mac OS X users.
Adblock Plus is one of the most popular Firefox Add-ons in the world, with over 10 Million daily users and over 100k downloads a day. They use phpBB to offer support to their users.