during summer, i like to cruise around with oldies playing. elvis, buddy holly, beach boys, etc.
otherwise, country or rock. I've been playing the crap out of the dark knight soundtrack on my way to and from school lately. couple of my favorites:
Nickelback
Hinder
GNR
Alan Jackson
Rascal Flatts
Eric Church
Keith Urban
if you like alesana, devil wears prada, underoath, etc... listen to Our Last night. their screamer is only 14 but good as hell.
some kid rock, johnny cash, shinedown is good for cruisin
but sometimes you just want to chill with some jack johnson, red hot chilipeppers, sublime, and dispatch