Let's see I'll try to define most of my mainstream picks
The Offspring-Alternative/Skate Punk
Green Day-Alternative/Punk
Weezer-Nerd Rock/alternative
Nirvana-Grunge
Foo Fighters-Rock
Trapt
AFI-Goth Rock/Punk/alternative
Journey
Van Halen-70/80s rock
Pearl Jam-Grunge
The Donnas-Female group
Story of the Year-Screamo/Punk
Stone Temple Pilots
Sum41-alternative
Sublime
Sugarcult-punk
Poison-80s rock
Motley Crue-80s rock
Three Days Grace
Flogging Molly-Celtic Punk
Sex Pistols
I'm personally not a big fan of Bands like the Killers, White Stripes, stuff like that. I like hard fast driven stuff.
I have some non mainstream stuff recommendations as well, well at least its not mainstream over where I live.
The Classic Crime
Goldfinger-punk
All time Low
Homegrown
The Adored
Quietdrive
Nightwish
Dragonforce
Less then Jake-Ska