Trail improvements, interpretive programming, historic preservation, and even transportation are some of the projects tackled by national park friends groups year-in and year-out. With time running out in 2013, consider a year-end tax deductible donation to your favorite friends group to help them through 2014.

By donating directly to a friends group, you can be sure your dollars will be put to work in the park of your choice. How are the funds used? Here are some examples (click on the friends group's name to go to their website to make a donation):

* At Acadia National Park, Friends of Acadia has raised, and spent, millions of dollars over the years on projects as diverse as the Acadia Trails Forever program, the country's first endowment program that benefits the park's 130 miles of hiking trails, and the Acadia Youth Technology Team that works on 21st century programming to entice today's youth into the park.

* Friends of Saguaro National Park uses donations to its Adopt a Saguaro fund to help underwrite research into research "the complex ecological interrelationships that govern the health and character of saguaro stands" in the park. Donations also go towards studying the park's mountain lions; the "madrona pools," perennial water sources in the park, and; archaeological research.

* Washington's National Park Fund tends to the needs of three parks -- Olympic, North Cascades, and Mount Rainier. This non-profit has invested $15,000 to revegetate the North Fork and South Fork camps in North Cascades National Park, $50,000 on volunteer programs at Mount Rainier, and $50,000 to help provide winter access to Hurricane Ridge in Olympic. And those are just three projects out of dozens tackled in the past three years alone.

* The Zion Natural History Association keeps busy working on behalf of not just Zion National Park, but also Ceder Breaks National Monument and Pipe Spring National Monument. Through books, clothing, and other park-related items sold in its bookstores, the Association invests approximately $600,000 a year in the three units. One-hundred-percent of the donations to the Association's Adopt-A-Bighorn program goes into Zion's bighorn research program.

* You also can "adopt" wildlife from the Yellowstone Park Foundation, which invests proceeds from those programs back into wildlife research projects in Yellowstone National Park. Or, you can benefit campers by investing in 'bear boxes" that are used to keep campers' foods away from bears.

* The Buffalo National River Partners in Arkansas helps pay for hiking trail maintenance, serve as a watchdog concerned about such things as a hog farm located upstream of the national river, contributed towards restoration of furniture at the Buffalo Point cabins and lodge, and works to connect kids with the park.

* The Appalachian Trail Conservancy pays attention to the 2,180 miles of the Appalachian Trail. The Conservancy organizes trail maintenance crews, educates hikers on being good stewards to the landscape, monitors the boundaries to the A.T. to ensure they're not infringed upon, and works to engage youth in the outdoors.

* Friends of Mammoth Cave National Park in Kentucky works on bringing school children into the park via transportation grants, supports a "visiting scholar" program that brings researchers into the cave, and is growing an endowment program to "fund summer internships providing students with 150-200 hours of work experience. Interns would be involved in an educationally and scientifically challenging program to assist with on-going research within the park."

* Friends of Apostle Islands National Lakeshore in Wisconsin has helped underwrite the Raspberry Island Boathouse Restoration, printing of the lakeshore's newspaper, and providing a matching grant for the Real Time Wave Observation System at the Mainland Sea Caves. The group has worked to raise donations, in part, by selling nightime photographs of the lakeshore's lighthouses.

* Friends of Canaveral is dedicated to helping out Canaveral National Seashore in Florida. The organization has helped restore historic buildings there, contributed to interpretive programs, and participated in the 2013 Canaveral Seashore Paint Out – a celebration of plein air painting at the seashore.

* In Massachusetts the Friends of Cape Cod National Seashore helps fund educational and interesting lectures for summer visitors, has helped with the restoration of the historic Penniman House grounds, and provided wayside signs along the Province Lands Bike Trail, among other projects.

* Friends of Big Bend National Park stays busy on an array of projects at the national park. The group has commited to raise $350,000 for the Fossil Discovery Trail, contributed more than $100,000 for restoration efforts at the Rio Grande Valley wetlands area, and raised more than $200,000 for a new visitor orientation film.

* Blue Ridge Parkway Foundation garners much attention with its TRACK Trails program that literally lures youth into nature. But the organization also helps underwrite concerts at the Blue Ridge Music Center, helps with restoration of the Graveyard Fields area, and has made live weather reports from the Parkway available to visitors before they leave home.

* The Grand Canyon Association takes on multiple responsibilities at Grand Canyon National Park, from underwriting on-the-ground projects such as the restoration of the Bright Angel Trail trailhead area and renovation of the Kolb Studio to creating "virtual museums" that, through the use of digital collections of artifacts and historic photographs, are made available through the American Southwest Virtual Museum website.

* The Grand Teton National Park Foundation is currently working on a $16 million public-private campaign to restore the Jenny Lake area in the park with improved bridges, trails, and interpretive materials. But the foundation also has an acclaimed Youth Conservation Program, has created a Discover Grand Teton website so you can familiarize yourself with the park before visiting, and is planning to raise funds to create an appropriate museum area for the Vernon Collection of Native American artifacts.

* In Montana, the Glacier National Park Conservancy underwrites wildlife research, conducts citizen science programs, invests in research on wildlife connectivity corridors, spends money on trail rehabilitation and maintenance projects, underwrites a native plant nursery, and works on the preservation of historic photographs. Among other things.

* Currently the Channel Islands National Park Foundation is working to make folks aware of the draft General Management Plan for the national park that now is open for public comment. But the non-profit also has worked to restore the Channel Islands fox to the park's islands.

Can't settle on one national park? Consider making a donation to:

* The Coalition of National Park Service Retirees, a group of more than 900 former National Park Service employees that advocates on behalf of the parks. You can support their cause by donating at this site.

* The National Parks Conservation Association also advocates on behalf of the entire National Park System and the National Park Service. You can support their efforts via this web portal.

* The National Park Foundation is the National Park Service's chariable arm, and works to raise money for projects and programs in the National Park System. You can donate to that organization at this site.

Finally, while donating to National Parks Traveler isn't tax-deductible, if you value independent journalism that focuses entirely on national parks, and appreciate a daily dose of news/features/commentary dedicated to the parks, help keep the Traveler online by becoming a member for $9.95. Membership benefits include being able to contribute to, and benefit from, Parkipedia, participating in forums with fellow park travelers, and benefiting from discounts on lodging, book purchases, outfitted trips, and more.