Let's see...I've been to quite a few concerts, some I wish I had missed.
Neil Young and Crazyhorse (very first concert ever...it sucked, but I was 12)
The Pointer Sisters
Rod Stewart
Milli Vanilli (so humiliating to admit this) and Young MC
New Kids on the Block (2 times)
The Cranberries (3 or 4 times)
Toad the Wet Sprocket
Counting Crows
Live (2 times)
Madonna (2 times)
Depeche Mode (2 times)
U2
Republica
3-11 (4 times - awesome in concert)
Bush
The Wallflowers
Cake
Orbital
The Cure (Robert Smith was old and fat, kind of sad)
Duran Duran (SWEET!)
Bow Wow Wow
The Psychadelic Furs
Peter Murphy
Violent Femmes
Beck
Smashing Pumpkins (before they broke up)
Garbage (3 times)
Dashboard Confessional
Fountains of Wayne
Soft Cell
Interpol (AWESOME!)
Echo and the Bunnymen
Hot Hot Heat (2 times)
Fishbone
Deep Blue Something (free concert at CSULB)
Dramarama
Jet
Presidents of the United States of America
Eels
Siouxsie and the Banshees
Linkin Park (5 times, once with Jay-Z - that was f-in awesome)
No Doubt
Alanis Morissette
Everclear
Staind
Static-x
Deadsy (horrible!!!)
STP (before they broke up, but after Weiland layed off the sauce)
POD
Hoobastank
Jurassic 5
I'm sure there are more bands, I just can't think of them right now.
ETA: Pink Floyd (How could I forget the PF?)
Veruca Salt
Goldfinger
Marky Mark + FB
New Found Glory
Blindside
Threaded Mode