How do your groups keep track of trip expenses? We generally take turns paying for stuff and then try to add it all up later...which is always sort of a headache. I've thought about using a kitty, where everyone throws in some cash, but it's usually just easier to use a credit card at the pump, etc. Or maybe having a kitty and using only one person's credit card so that person can add it up easily after the trip is over. We normally split gas and food evenly as we all tend to use about the same of each...