If you are wondering about rv volunteer opportunities, ask yourself the following questions: Are you willing to serve in a position with no salary, no stipend, little or no remuneration other than incidentals?
If so, become an rv volunteer in the National Park Service. Many of the federal agency opportunities listed here offer housing, or RV pads with electric/water/sewer hookups in return for the hours you work. This site is where I found my first job working with the maintenance department at Organ Pipe Cactus National Monument, and my second job as an interpretive guide at Petrified Forest National Park. My third job, at Kodachrome Basin State Park, started out as volunteer camp host, but became full-time, as a ranger aide.
At Organ Pipe NM, my rv site had water, sewer and electric hookups which is pretty standard. They also filled my propane tank as often as I needed it done. Petrified Forest did not cover the propane, but paid a $5 per diem. So, make sure you ask questions to find out exactly what the park is giving you in return for your hours.
I loved the year I spent volunteering, and learned so much!
Maybe you have skills or knowledge you’d like to share with the visitors at a beautiful location for a couple of months or more. There are various rv volunteer opportunities offered and the NPS website has an excellent search function, so you can fine-tune your search to zero in on a particular state, or a particular category of opening (for example: geology, archaeology, or weed control), or a specific type of agency, i.e. national forests, wildlife refuges, BLM.
You should also check out websites of state and local agencies for rv work opportunities. I filled out an online application which I submitted along with my resume to Utah State Parks, after deciding I really wanted to spend some time exploring Utah. I received a nice acknowledgment from the main office and, a week or so later, a call from a ranger at a state park near Bryce Canyon. That resulted in an rv volunteer opportunity (which transformed into a full-time ranger aide job) for the second half of summer 2011. Most states are experiencing budget shortfalls and are having trouble staffing their parks. They really need us!
When you visit a park during your travels, if it is one where you
would like to spend more time, make a point of talking with the ranger
or camp host and let them know you would be interested in working there.
Fill out an application for them to keep on file. The most popular
parks get lots of applications and you may have a better chance of
success if they have actually met you. Check out the nearby towns as well - you may find an opportunity that would keep you in the vicinity of your favorite park.
Check organizations like the Elks and Lions in areas you're targeting. They often need help with their booths at county fairs. In the West, there are "dude" ranches for under-privileged kids that offer volunteer opportunities. You never know what you might end up doing, and you'll probably have a lot of fun. How about a cattle roundup in WY? I've barely scratched the surface on this page. Do your research - there are lots of possibilities.
Other opportunities for volunteering that may be of interest to you:
RV-Care-a-Vanners at Habitat for Humanity
How to survive a summer in Tucson.