Cool thread, first off...
I would do just about anything if it were possible for me to go back in time and see bands like Pink Floyd, Zeppelin, the Stones, the Dead, etc during their prime...alas
Anyways, here's my list, the best I can remember it (and in no order):
Phish (23 times)
Medeski Martin and Wood (10+)
Umphrey's Mcgee (10+)
Karl Denson (5?)
Sound Tribe Sector 9 (10?)
Oysterhead
Trey Anastasio (solo)
Les Claypool's Flying Frog Brigade
Phil Lesh and Friends (3?)
Tool
Smashing Pumpkins
Tom Petty
Bob Dylan
String Cheese Incident
Leftover Salmon
Roger Walter's 20th Congress
Tea Leaf Green
Soulive
Disco Biscuits
Keller Williams
Yonder Mountain String Band
Dark Star Orchestra
Michael Franti & Spearhead
Jacob Fred Jazz Odyssey
OM Trio
Steve Kimock
Steve Winwood
John Scofield
Fareed Haque Group
The Slip
I could keep on going, but that's a decent list...I enjoy a lot of smaller bands that tour hardcore and rely on word of mouth to be successful. I enjoy the improvisational aspects of live music and appreciate the bands that play show after show (each of them different) for their fans.
GO SEE LIVE MUSIC!