These particular "top 5" are the hardest. Currently there are dozens of active Spuffy archives with regular updates, boards and forums. I got terrible headache trying to narrow down the list and almost gave up. Still I decided to make a try. I post a pretty random "top 5" and beg the owners of other wonderful, wonderful Spuffy archives to forgive me for not including them in the list.
So, in no particular order...
Vampire's Kiss
http://vampires-kiss.net/archive/index.phpBloodshedverse
http://www.bloodshedverse.com/index.phpElysian Fields
http://www.dark-solace.org/elysian/index.phpThe Spuffy Realm
http://www.spikeluver.com/SpuffyRealm/index.phpThe House of Bloodshed
http://www.bringonthebloodshed.com/