We usually listen to bluegrass. Sometimes I'll get so involved in the fiddle or mandolin line that I'll drive right by where I'm going :-).
We also have the New Testament on CD ("The Bible Experience," new recording that came out last year) and we've been having a great time with it. It's full of personality. Our favorite so far (we've been listening to parts of Gospels and letters at random) is St. Peter, who sounds like a tobacca farmer frm over t'Marshvlle.
"And a little after, they that stood by said again to Peter, Surely thou art one of them: for thou art a Galilaean, and thy speech agreeth thereto."