Really diggin' Phoenix right now. I think Lasso is my favorite song of theirs so far.
alternative is such a broad genre though and there are so many that are good. muse, radiohead, jimmy eat world, coldplay, if you count "grunge" as alt., then of course the big 4: nirvana, pearl jam, alice in chains, soundgarden. foo fighters, weezer, live... i could go on and on and on.
my alternative faves-Joy Division, New Order, Cocteau Twins, Siouxsie, Cabaret Voltaire, Nitzer Ebb, Laibach, Bauhaus, Pil, Psychic TV, Psychedelic Furs, The Charlatans, Blur, The Specials, Madness, The (English) Beat, Echo & The Bunnymen, Throbbing Gristle, Gene, Inspiral Carpets, Chris & Cosey, Severed Heads, Stone Roses, The Sugarcubes, Front 242, and many more.