What We Like: 
We love how easy and intuitive this Active-powered app was built to be. With Recreation.gov Camping, users can easily discover their next camping site based on availability and campground details for upcoming summer trips to National Parks, Forests and other Federal Recreation Facilities.
Why it's cool: 

Recreation.gov Camping lets you locate available Campsites at National Parks, Forests and other Federal Recreation Facilities. Perfect for the avid Camper or RV'er looking for a place to stay, today. Instant availability information on Campsites, Cabins, Day-use and other sites. Check for today's availability or for future Reservable dates. Save your search settings to make finding your next stay as easy as opening the App. View Campground details, including the details of each available Campsite. View Photos to help you pick your ideal spot. Reserving your spot is just a touch away to the Recreation.gov website or to the NRRS Call Center.

API: 

http://developer.active.com/

Application URL: 

http://itunes.apple.com/us/app/recreation.gov-camping-find/id490668237?mt=8

Platform: 
iPad
iPhone