when driving virtually, i take whatever the game offers- so no music in SD... but i really loved the soundtrack of (wiki article tells that i have not been the only one to love it
).
when driving in real world (no racing, just traffic..), i usually prefer classical music, as this keeps me relaxed and prevents me from fretting about other drivers' behaviour...
only when driving long distance trips (preferably at night, because Autobahn is empty at this time and you can drive fast), i have some tapes with good old 90s techno