If "milk does a body good," then the plastic jugs which contain the milk, do a wagon good. Check out this wagon, made from recycled plastic milk jugs. Its name is as big as its earth friendliness factor: Recycled Plastic Radio Flyer Earth Wagon. Instead of trying to degrade in a landfill, 230 milk jugs were used to make its body. Due to its composition of 100% recycled plastic, it won't need painting and it won't splinter or rot like some of its wooden counterparts.
The sides are removable, so you can wheel your kiddies around, or if you live near your grocery store, save the earth from car fumes and walk, using the Earth Wagon as a way to lug home your loot.