I know that some Airstreamers volunteer their time at National and State Parks and a variety of other resources. I did some searching and didn't see much on this so I thought I would start a thread on it.
I worked as a California State Park Interpretive Ranger a lifetime ago, an interest that has been rekindled. Vicki is a gamer when it comes to this kind of thing as her father was a Park Ranger when she was growing up and she spent more than one summer as a fire spotter atop fire lookouts accessible only by horseback.
There are many, many volunteer oportunities: interpretive ranger, campground host, helping in stores and kiosks, etc. The best place to find them is at Volunteer.gov - http://www.volunteer.gov
It would be great to hear from others who have done volunteer activities. Vicki and I have our first gig in October serving as Lighthouse Hosts at Cape Blanco Lighthouse on the Oregon Coast. Come on by!