We have also listened to a few audio books on CD while driving long distance. Any time you can get your hands on an audio book of Tony Hillerman's series on the Navajo Tribal Police read by George Guidall, do it. We listened to The Wailing Wind one trip and now all I hear when I read Tony Hillerman is the voice of Guidall. Luckily, it's a beautiful voice, so that's a good thing.
And then there's Max Brooks' World War Z: An Oral History of the Zombie Wars. It's a fun book to start with, but then when you add the voices of people like !!MARK HAMILL!! reading characters, it rises to the level of awesome. It's abridged, and there were a couple of my favorite chapters that got left out, but over all, I highly recommend it.
I'll also put in a plug for any of Judy Kaye's readings of the Sue Grafton alphabet mysteries. She gets Kinsey Milhone beautifully.