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.
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.
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.
Active community for UK based Audi TT owners. Almost 30k members and 2 million posts, complete with unique style & powered by phpBB.
Independent site for Dutch horse lovers. With over 280,000 members and 95 million posts, Bokt.nl is widely acclaimed as one of the largest boards powered by phpBB.
Support for Synology NAS devices and ideas for future versions of the DiskStation software.