Too many to recall, but in no particular order:
Joe ****er - first concert ca. Spring '71 Madison Square Garden
West, Bruce and Laing
James Gang
Grateful Dead - many times
Pink Floyd - several times
Zappa - several times, first being 11/74
Harry Chapin
Allman Bros
Weather Report
Chick Corea, Return To Forever and solo
Larry Coryell and the Eleventh House
Chick Corea and Gary Burton - several times, grand piano and vibes,awesome!
Dave Brubeck
Oregon
Ralph Towner and John Ambercrombie - GREAT show!!!
Hot Tuna/Jorma - numerous times
Miles Davis
Moody Blues
Warren Zevon
Jerry Garcia Band
Clapton
Yes - HS English class field trip organized by yours truely

Plenty of bluegrass
Drew Emmitt (lives here in Crested Butte)
Leftover Salmon
Richie Havens
Mahavishnu Orchestra/Shakti
Stanley Clark - several times
Brecker Brothers
Tower of Power
J Geils
Savoy Brown
Jefferson Starship (wish it had been the old Airplane, but so it goes)
Phish (didn't like)
Andre Segovia
Willie Nelson
Derek Trucks
Tom Scott and the LA Express
...the list goes on