phpBB.com  Creating Communities
phpBB (PHP Bulletin Board) is the leading free open-source bulletin board package. Create an online community on your website today! phpBB is a high powered, fully scalable, and highly customisable open-source bulletin board package. phpBB has a user-friendly interface, simply and straightforward administration panel, and helpful FAQ. It is based on the powerful PHP server language and a choice of MySQL, MS-SQL, PostgreSQL or Access/ODBC database servers which makes phpBB the ideal free community solution for all web sites.

Forum Software / Message Board Software:
Guide to Software for Discussion Forums, Message Boards, BBS / Bulletin Boards, and Groupware, for Intranets and the Web. Web Forum Software: Comprehensive guide to software that powers discussion forums and message boards on intranets and the Web, including BBS software, groupware, and software for virtual communities.

vBulletin® - Instant Community
vBulletin is a powerful, scalable and fully customizable forums package for your web site. It has been written using the Web’s quickest-growing scripting language; PHP, and is complemented with a highly efficient and ultra fast back-end database engine built using MySQL. vBulletin is the ideal community solution for all medium-to-large sites.