Best Road Trip Hints for Kids?

I’m hitting the road with the kids at the end of the week, not to Washington, D.C., as originally planned, but to the Badlands and Black Hills of South Dakota.  (I decided we’ll go to D.C. when the kids are a bit older.)

So, I ask you, dear readers, for the best road trip games for kids.  I’ve already printed out some road trip bingo cards, and the license plate game.  Any other ideas?

And how about favorite audio books — or, better yet, podcasts (free!) for the trip?

Really, any tips for the road trip?