There is an open source forum based on php together with MySQL

YABB (just another bullentin board)

I think it rocks.. but then again, who am I?

(there is also a pure cgi-version available in case Php with MYSQL is not your taste)


if you are curious check out : http://www.yabb.info/community/
(well there you can also see the forum at work but keep in mind that nearly everything is possible)