I really like the thought behind this thread here goes the list
Jack Johnson, Rancid, Dropkick Murphys, Led Zeppelin, Nirvana, White Stripes, Weezer, Transplants (a little bit), The Clash, Weird Al, The Vines, The Hives, Jet, U2, Suicide Machines, Sublime, The Sex Pistols, Rolling Stones, Beatles, Red Hot Chili Peppers, Outkast, Ludacris, NIN, Neptunes, Metallica, Libertines (in the UK anyways), Jurassic 5, Iced Earth, Mos Def, Gorillaz, Foo Fighters, Moby, Fatboy Slim, Cake, Bush, Beck, Ben Harper and the Innocent Victims, 311
I tried to keep it slim, since I normally have a very broad idea of mainstream. For example, I would have put Catch22, but they're only mainstream in the ska scene.