UseBB is a PHP/MySQL forum package. Unlike other popular forum systems, it does not strive to have as many features as possible, but to be one of the easiest and most usable forum packages, limiting the basic feature set to only the essential. It is an ideal solution for small to medium-sized Web sites which require an easy to use forum package without the bloat, that produces standards compliant output, and is secure and easily configurable.
MyBestBB is a full-featured forum based on punBB. It adds many features, modifications, and themes to the default punBB, including RSS feeds, UTF-8, XHTML 1.0 strict compliance, sub-forums, PMs, attachments, rewrite rules, the ability for an admin to move posts, easy smilies, easy polls, many improved themes, announcements and sticky topics, an activity barometer, a URL rewriting module, and much more.
Nearforums is a lightweight powerful discussion forum that can be installed within minutes on Linux or Windows servers with MySQL or MS SQL database servers. It includes great features like sign-in with Facebook/Twitter, navigation with tags, full Web administration, built-in search engine, RSS feeds, and accessible HTML. It is SEO friendly.
OpenLaunch is a Web-based content management system that integrates a broad array of services into a single, fully-featured, elegantly designed Web site. The project aims to eliminte the difficulty of integrating multiple systems into a single Web site by implementing a blog, forum, Web pages, wiki, and (coming soon) E-Commerce and support tickets. It is built around the Torpedo Framework, an open MVC framework which includes support for controllers, forms, and a large number of other very useful utilities.