phpBB: Official site, offering news, support, and downloads of the forum software, modifications, and templates

vBulletin: Features templates, import messages from other systems, search, unlimited forums, email notification, smilies, user profiles, moderators, user groups, private forums, word censor, private messaging, and user ban. [Commercial

vBulletin.org: Official vBulletin modifications website. Free plugins and modifications are available

Woltlab Burning Board: Bulletin board software based on PHP4 and MySQL. Some of the features: HTML Templates, User profiles (editable by user), User groups, and BB Code or HTML in messages. Available in English and German