Some years back I bought my wife one of these folding aluminum carts for the barn:

http://www.tipkemfg.com/

but it ended up staying in the garage and we put it in the truck s whenever we think we might need to haul gear for Scouts (when we have to park a good distance from the camp site) or other activities. They even make a marine-grade version in case you want to use it along the sea coast.

It folds easily and hold a lot of gear. I don't think its quite as tough, nor quite as big as the non-folding barn carts such as this:

http://www.norwaycarryall.com/carryall.html

but the aluminum cart folds fairly small and works well for us.