Discussion board for the massively popular xkcd web comic. Covering everything from Maths and Science to Logic Puzzles and Forum Games. Over 100k members and 2.4 Million posts.
Developed by Focus Home Interactive, Cities XL 2011 is a city simulation game. Their community forums are powered by phpBB.
OpenOffice.org offers a free and fully-featured office suite which meets the needs of the common consumer all the way up to large enterprises.
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.
Support for Synology NAS devices and ideas for future versions of the DiskStation software.
Pixelmator is a popular commercial image editing software for Mac OS X users.