License Plate Bingo
The best way, in my opinion, to keep kids occupied on a road trip without having to resort to the in-car television is to have a rousing game of "license plate bingo." Not only does it keep the kids occupied for the entire trip, but it also teaches them about all the different states.
All you have to do is make bingo boards for your kids and let them fill in the states the night before the trip. Once you get on the road, they will spend their time trying to get "Bingo."
Best of all, unless one of your kids is particularly apt for geography, the odds of someone winning before the trip is over are very slim, guaranteeing a fun game that lasts for the ENTIRE car ride.