Other great jam bands/Artists:
Gov't Mule
Widespread Panic
North Mississippi Allstars
Guster
moe.
Keller Williams
Michael Hedges
Allman Brothers
Grateful Dead
Oysterhead
String Cheese Incident
Yonder Mountain String Band
OAR
Wilco
whether you like to admit it or not Dave Matthews band pre-1997 or so.
Tool... I don't care what you say... Tool is a jam band.
I'm going to Bonaroo this year... perhaps the Mecca of Jam bands.