Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
phpBB - Raspberry Pi. The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums. phpBB is not affiliated with nor responsible for any of the sites listed on the showcase.
Flarum - Flarum is the next-generation forum software that makes online discussion fun. It's simple, fast, and free.
XenForo - Intuitive. Social. Engaging. Fast. XenForo brings a fresh outlook to forum software.
Vanilla Forums - Build an engaging community forum using Vanilla's modern cloud forum software.
FluxBB - FluxBB is a fast, light, user-friendly forum application for your website.