vBulletin - Build a community website with the leading forum software, vBulletin 5 Connect, or in the cloud on vB Cloud!
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.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
Simple Machines Forum - Simple Machines offers free open source software such as SMF, the powerful and easy to use community forum written in PHP. Start interesting discussions on your website!
MyBB - MyBB is a discussion board software that runs on PHP and MySQL