Pay it Forward Private Campsite Swap

My wife and I would like to explore different parts of the country for a few days at a time. The cost of a commercial campground can really add up, especially when you don't care about all the extras like swimming pools and such, and only use your camper for a home base when you're not out exploring. I wonder if there are any groups in existence where country folks can offer you a place to dry camp for little or no money. In exchange, you offer your hospitality to others.

We have several spots on our farm in southern Ohio where folks could park a camper for a few days at a time. There are several water hydrants around the farm, and some of them even have electric nearby. Sure beats a Wal-Mart parking lot. What do you think? Do such exchange groups already exist and I have not found them?