Originally Posted by Psy-Fi

Probably forgetting some headliners as well as opening acts, but...

Allman Brothers Band (x35)
Jeff Beck
Black Sabbath
Blue Oyster Cult
David Bowie (x5)
Cheap Trick
Clash (x2)
Cream
Cure (x4)
Don Felder
Firm
Peter Frampton
J. Geils Band
Grateful Dead
Buddy Guy
Eric Johnson
B.B. King
Sonny Landreth
New Order
Ted Nugent
Page & Plant
Pink Floyd (x3)
Primus
Public Image Limited
Red Hot Chili Peppers
Rolling Stones (x6)
Santana
Silverchair
Sugarcubes
Talking Heads (x2)
George Thorogood
Traffic
U2 (x2)
Stevie Ray Vaughan
Who
Steve Winwood
Neil Young (solo, with Crazy Horse, With Booker T. & The MG's, With Pearl Jam minus Eddie Vedder.)
Frank Zappa (x2)
ZZ Top (x2)

Also saw the first Lollapalooza and attended the Reading Festival in 1992, 93, 94, 95, and 96, and saw the 1998 Guinness Fleadh Festival.