Here's some good clean mainstream alternative, more or less: Staind, Tool, Incubus, Godsmack, A Perfect Cirlce, Creed, Fuel, Linkin Park, Alice in Chains, Radiohead, Our Lady Peace, Pearl Jam, Lit, Everclear, Collective Soul, Bush, Deftones, Nirvana, Oasis, Nixons, 3 Doors Down, Stone Temple Pilots, Weezer, Toadies.
If you wanna get into ska/punk try: The Impossibles, Less Than Jake, Mighty Mighty Bosstones, Five Iron Frenzy, No Use For a Name, MxPx
or more hardcore:
Jack Off Jill, Slipknot, Sevendust, Disturbed
or Rock/Rap:
Cypress Hill, Everlast, Eminem, Limp Bizkit, Rage Against the Machine