Stuff I like:
Alternative: Radiohead, Muse, Gomez, Tool (which is more metal), The Dandy Warhols, Coldplay, Red Hot Chili Peppers etc.
Electronica: Aphex Twin, Autechre, Boards of Canada, Plaid, Massive Attack, Prodigy etc.
Post-Rock: Sigur Ros, Godspeed You Black Emperor, Mogwai, Tortoise...