If you want to groove out to the tunes you hear in the game while you're at work or in your own real car, you can snag a boxed-set of most of the tracks. Just like in the game, they're split up into stations. The soundtrack for each disc/station is listed here (there are some songs that appear in the game that aren't on the discs):
"No New Tale to Tell" by Love and Rockets - As Charlie wanders around the party high and looking for the bathroom, this song plays as he accidentally walks in on Patrick and Brad (Johnny Simmons) kissing. Their secret and complicated relationship is reflected in the song's lyrics.
"Here" by Pavement - This song plays as Charlie is officially welcomed into the inner circle of Sam, Patrick and the so-called "island of misfit toys." Patrick gives a speech honoring Charlie and his ability to sit back and observe the world around him, dubbing him a wallflower. It is a turning point at Charlie is accepted like he has never been before.
"Counting Backwards" by Throwing Muses - Charlie's relationship drama with Mary Elizabeth comes to a head when he kisses Sam at a party instead of her. While it causes more than a little time to blow over, Mary Elizabeth eventually gets over it and tells Charlie she is now dating Peter as this song plays.