ForensicsOnline.Net: Has a good message board that old and new competitors frequent daily to provide feedback and theories on extemp and other events.
National Forensic League: Site offers old Rostrum articles that discuss extemporaneous speaking and it gives information to extempers wanting to purchase old national final round tapes even though they will cost you a pretty penny. Two of the best rounds I have seen are the 2000 and 2003 IX final rounds.
Speek Geek: A site run by my friend Corey Alderdice. If you ever want some "speech gear" this is the place.