Here are a few items we found indispensible on our road trip. Highly recommended for those travelling in a car for any considerable amount of time.
Igloo KoolMate 40 This is a thermoelectric cooler/heater which plugs into the cigarette lighter in the car. It cools to something like 45 degrees below outside temperature or heats to 155 degrees. It was the perfect size for keeping all of our lunch foods cold on the drive.
Earthmate GPS Receiver in combination with the Delorme Street Atlas allowed us to trapse all over the place without the worry of getting lost. The trip planning portion of the software makes some questionable decisions, but the capability of knowing exactly where you are at all times is priceless. We borrowed this from a friend of my dad’s but are planning on buying it for ourselves since it was so useful.
We also borrowed my dad’s XM Radio so we didn’t have to deal with searching for radio stations every 15 minutes. I don’t have a need for one all the time, but it’s great on trips.