You haven't heard of this music, but you should have:
Of Montreal: I've mentioned before that Of Montreal is mindblowing. I love them even more now that I've listened to almost all of their albums a few times. And like any great band (and unlike shitty bands), they've evolved over the years, but managed to keep a core of awesomeness.
Infected Mushroom: Some may think it's cheesy to blatantly mix genres of music, but I fucking love this combination of bass-heavy trance, heavy metal, and some cheesy pop-goth vocals.
LCD Soundsystem: My friend Jard was like "you gotta listen to LCD Soundsystem", so I did, and I was like "this is really boring", but then I listened again, and I was like "maybe I was dumb before, because this isn't so bad", and then I listened again, and was all like "if I were a squirrel and LCD Soundsystem were a nut, I would bury it in the ground and dig it up every night to cuddle with and nibble on."
Modeselektor: These guys make very strange electronic music. It's alright. I only include them on this list because one of the songs on their latest albums features Thom Yorke, who makes all music great.
The Sword: I discovered these guys through their song, Freya, in Guitar Hero II (and to a lesser extent, through Lyndsay Lohan getting semi-naked to it in her wonderful movie, I Forget Who Tried to Kill Me). I'm glad I did. This music will rock your face off, then rock your ass off, and then your ass and your face can rock out together on the floor. The music is similar to Wolfmother, which is to say, similar to a combination of Black Sabbath and Led Zeppelin. The lyrics are obscure references to Norse mythology and George R. R. Martin, which is to say, awesome.
Britney Spears: Oh sure, you've heard of Britney Spears; she's that redneck drunk chick who shaved her head and flashed her vag and has a pregnant baby sister. But did you know that she also makes music? And really, it's not bad music. Not good either, but if you're at all into pop or dance music, you could do a lot worse. Her latest album, Blackout, even takes some shots back at the media that's ruining her life with songs like Piece of Me and Freakshow. She probably didn't write them, but hey, you can't expect shitty pop musicians to actually be musicians.