The latest version of phpBB has gone gold recently. It looks good and could be useful, although I've not used it yet. Its hard to find the new features list so here's the link:
http://area51.phpbb.com/docs/features.html
Highlights of what's new or greatly improved:
Automatic image thumbnails
Topic merging, topic copying
Locking of single posts
Users can report topics and posts
Moderators can warn users
Search inside topics, bookmark topics
"You got beaten at posting" notification
Attach files to PMs
PM folders, PM filters
Set temporary bans, comments for bans
phpBB3
Moderators: Moleman, Kwijibo, Luna