Facebook PunBB is a modified version of PunBB 1.2.20. It allows Facebook users to login with their Facebook account instead, and can be setup as either a stand-alone forum or a Facebook application. In either setup, it features:
*Automatic registration (and automatic login for the Facebook application setup)
*Link to the Facebook profile with the profile picture
*A new BBcode "quote_facebookID" for quotations
Moreover, the two setups can share the same database such that the forum provides seamless experiences for Facebook users while stays indexable by the search engines. The live demo (doubles as support forum for now):
*Stand-alone setup
*Facebook application setup
The patches are available here. It's licensed under GPL (pending sourceforge project status).
Special thanks to Chroma Coders for encouragement, advices, and hosting.