311 was my first concert, way back in November 1997. I've only seen them one other time, but I will say they're a great live band. I don't think they've put out a good studio album since Transistor (each of their subsequent albums have had some decent songs, but no entire album has been solid), but if you even remotley like them, they're worth seeing live. They're constantly switching up their setlists (not just a few songs, but usually 8-12 songs each show) and are great musicians.
02/25: Cannibal Corpse/Behemoth (?)