Just about all state parks use volunteers, either as campground hosts or as maintenance staff. In return for 24-30 hours per week they will offer a free campsite. Some will have full hook ups some will have water and electric. My wife and I have been traveling this way for 6 years now. I will usually call the park in the area where we want to travel to and talk with the volunteer coordinator. It will vary from state to state or even park to park within a state. If you have a particular skill that is usually a plus. Most parks will want 1-6 month commitment but most will be flexible. Another site is www.volunteer.gov this one will be mostly with federal agencies and the jobs will vary greatly. Always call to see what amenities are available and determine what is necessary for you. write out a list of what you require, wifi, cell phone service, local tv or cable. Ask all your questions up front and you'll be less likely to be disappointed upon arrival.