The Allman Brothers Band
The Gaslight Anthem
Gov't Mule
Gillian Welch
Dolly Parton (shut your smurfing face, Dolly is the sweetest human being alive and you will respect her or so help me)
JJ Grey & Mofro
Seether
One I'll have to think about.

On youtube you should all listen to Post Modern Jukebox (the Saturday Morning Slow Jams are especially great) and Puddles Pity Party/Big Mike Geier, because they're amazing.