I've travelled extensively in the south. The best places are out of the way, local establishments with a word of mouth following. I like ALL kinds of BBQ, so semantics over type be damned.
The following top my list;
Ridgwood Barbque - Elizabethton, TN
Moonlight Inn - Owensboro, KY
Mark's Feed Store - Louiville, KY
Rendezvous - Memphis, TN
Sonny's - Macon, GA