The Billy Goat Trail is one of the many sites that volunteers can clean up as part of National Public Lands Day. (Katherine Frey/KATHERINE FREY)

But let’s admit it, it’s kind of nice to get something a little extra.

In the case of National Public Lands Day coming up on Sept. 29, the good deeds range from picking up trash to planting trees to trail maintenance to painting cannons. The reward at most parks (again, besides the warm and fuzzy feeling) is a coupon for a free one day admission to a participating park for the coming year. And don’t worry about having to use it the day you volunteer, the admission fee is waived for everyone (volunteer or not) at most sites as part of National Park Fee Free Days.

And did we mention that many sites will offer their own special reward for volunteers? Think shirt giveaways, marshmallow roasts, panning for gold and demonstrations with National Park Service Dogs. A handful will even make sure volunteers are well fed. Some projects require registration, so check with the site before you go.