Oh... radio, I normally play mp3 instead, but if the opportunity's not there I'll flick over to NPR or whatever fairly often, least if it's doing music instead of news-y bits. Classical's always nice, and sometimes they do some neat other stuff... celtic/irish bits, various folk music, etc. Occasionally there's opera, which I don't take the opportunity to listen to very often. It can be nice. When I'm in larger areas there's usually a jazz station or two I'll be down with, too.
... but yeah, I don't drive much but family very often, most of which I avoid inflicting my mp3 player playlist on, but occasionally there's someone. Experience is still about how you mention it. Folks that say "whatever" tend not to actually mean they're down with high energy OCRemix followed by gospel (whether it's traditional or something like E Nomine, well...) followed by electroswing, remixed classical, literally elvis, drinking songs, and so on. The bright side is my playlists tend to be eclectic enough (and I play them on shuffle anyway) I can usually hit next a few times and hit something they're okay with. I just have to skip the stuff that'll probably give them literal headaches.
E: well, and the stuff like good ship venus. I've actually snuck that one in a few times but no one's noticed the lyrics yet. They've noticed baltimore whores, though :V