Use the desk area organizers you find at WM to hang on the back of the seats in the car - kids' road trip bags!! Could use for every day things too, like germ-X, wipes, etc. This blog entry has some GREAT ideas for keeping kids happy while road tripping!
In this Instructable learn how to make a portable camping shower. What sets this apart from a regular shower is it's pressurized so no need for a gravity feed bag that you hang from a tree, make this shower truly portable. This shower is super useful and is great for washing off after a day at the beach or after surfing. Or it can be used to water plants, especially useful if you have a rain barrel and need a way to get water to your plants.