Facebook Chat:

A plugin is available for Facebook in Pidgin at http://code.google.com/p/pidgin-facebookchat/

Facebook Chat is not officially supported in Pidgin because Facebook is working on exposing an XMPP interface to the world. (See: http://developers.facebook.com/news.php?blog=1&story=110 and http://bugs.developers.facebook.com/show_bug.cgi?id=3152) When that's done, Pidgin will support Facebook Chat just like any other XMPP service