Bokt.nl
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.
Joomla Forums
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.
Mozillazine
Hugely popular Mozilla community providing support for Firefox, Thunderbird, Seamonkey and other well known Mozilla products. Over 350k members and 4 Million posts.
Fujitsu
Fujitsu is a hardware and IT services company focused on providing IT-driven business solutions. Their community forum is powered by phpBB.
Zend Forums
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.