I don't drive myself, though when I eventually get my license (on hold for now due to university) then I'll probably just leave Radio 1 (UK) on. Or Radio Aire, my local station here in Leeds. However, when my dad drives, he has CDs. Right now he has my mum's Take That CDs (which are awesome, The Circus is a brilliant album), Guns and Roses, and Queen. He's massive Queen fan (with good reason

).
However, he's also, for some reason, recently gotten into classical music. No idea why, he's always been a power ballad type of guy. Add that to the fact he recently had a new car, i.e. the latest version of the Land Rover Discovery, and that has a really loud and massive sound system. So he likes to dive along with Mozart or Beethoven or whatever at full volume. And anyone who's ever heard classical music knows how loud it is at the best of times. It's exceptionally deafening whenever I'm in the car, though he's half deaf in one ear anyway so it doesn't matter as much to him...