Sijio is a fast, high performance, easy to use and fully customizable PHP community script. It is equipped with all necessary professional tools and features to run a full fledged community site. Features include blogs, events, a forum, a gallery, polls, page management, user management, and RSS feeds, customizable Smarty powered templates, WYSIWYG editing of any content, easy picture upload, an unlimited number of attachments, and more. It is completely SEO friendly.
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.
TinyIB is a lightweight PHP image board which emulates the functionality of 4chan. If you use MySQL or SQLite, you can use it to create an efficient setup able to handle large amounts of traffic. If you don't use a database, it can store posts as text files for a portable setup capable of running on virtually any PHP host.
CodingTeam is a software forge that is lightweight and extensible. It provides a lot of collaborative tools. With this software forge, projects can benefit from basic features (such as screenshots, downloads, uploads, and news), communication features (such as chatrooms, forums, the OpenForge API, and Jabber/XMPP integration), and development features (such as a VCS code browser, a bug tracker, SVG statistics, timeline, and roadmap). Also provided are community tools (project browsing, tag clouds, notepad, and user profiles).
FluxBB is a fast, light, user-friendly forum application for Web sites. It was originally based on PunBB and supports UTF-8, XHTML, and internationalization, and leaves out some of the less than essential features of other forums without sacrificing essential functionality or usability.