National Park Service
If you're going to give your precious time as a volunteer, you might as well get some fresh air and sun while you're doing it. Roughly half the volunteers for the National Park Service (NPS), which maintains federal parks, monuments and battlefields across the country, are retirees. In 2007, approximately 163,000 park volunteers donated 5.4 million hours for a total value of more than $101 million -- the equivalent of 2,596 additional full-time employees [sources: National Park Service, AARP].
Park volunteers perform a wide variety of tasks. Yosemite National Park in California, for example, brings in volunteers to serve as mentors for kids participating in its Youth Conservation Corps. Meanwhile, in Washington, D.C., volunteers provide information to visitors at sites like the Korean War Memorial and the Washington Monument. Additionally, the National Park Service's Artist-in-Residence program provides opportunities for artists to live and work in one of 29 participating parks [source: National Park Service].
Besides nature's splendor, some volunteer positions include perks such as a small daily stipend, meals and free access to RV pads. Volunteers who acquire 500 service hours are eligible for an annual pass that provides free access to all federal recreation sites [source: National Park Service].