I like cruising to instrumentals with a good beat, a little bass, & chill undertones...which ends up being either lounge or certain hip hop artists. If I'm in the mood for vocals I'll go for the hip hop (& some lounge), or if I don't want any vocals I'll listen to only lounge (majority of what I have has no vocals). When I'm not in the mood for those, I'll listen to my driving mix, and/or soundtracks...
Lounge artists:
Thievery Corporation
Zero 7
Morcheeba
Cafe del Mar
Kruder & Dorfmeister
Atmospheric Reflection
Royksopp
Hip Hop:
Blackstar
Roots
Atmosphere
Blackstreet
...and more like these guys
Soundtracks:
GTA: Vice City
Halo (lol)
Ironman, etc
Other standard music:
Fleetwood Mac
Tantric
Days of the New
etc
Of course it comes down to your taste in music...