OpenCart is popular, powerful, and easy to use shopping cart software. Their healthy community forums are powered by phpBB.
Official Support Forum for Debian, the kernel-based open source operating system. phpBB provides a solid platform for support and discussion.
KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
Fujitsu is a hardware and IT services company focused on providing IT-driven business solutions. Their community forum is powered by phpBB.
Pixelmator is a popular commercial image editing software for Mac OS X users.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.