A application developer has a map application for USFS and BLM campgrounds, iTunes Web page, which costs all of $2 in the iTunes app store. And while it's cheap, I have to say it's only about worth the money you pay for it.
The app is based on Google Maps and indexes of US Forest Service (USFS) and Bureau of Land Management (BLM) campground in western states. For that the app does a good job as well as providing links to additional information about each campground.
What I found to dislike about the app is that it doesn't save a start map and place when you open the app. It resorts to the world maps, then a map of North America based on your current location. You have to go to the "set current location" window to click the place you set for your preferred place.
This could be resolved by just saving the map and location information. The second is that, despite having a checkbox for "walk/hike in" campsites, it doesn't have any. All the USFS campground are all drive-in sites. Or at least the areas I've looked at.
The main area I checked was Mt. Rainier NP. All the campgrounds are accessible by car, and only those on maps of the Forest Service forest or Wilderness Areas around Mt. Rainier NP. This is in part because the backcountry campsites are only on other maps but are listed in guides and other publications.
This means detailed information isn't readily available to put into an app like this one. So if you're looking for backcountry campsites in USFS forests or BLM lands, this isn't the app for you. Your best bet is USGS topographic maps and hiking books.
The last minor inconvenience is that it leaves the icon on your dock. If you don't want it, you have to trash it and keep remembering to remove it everytime you close the app. This should be a user setting or not keep it and let the user put it there from the applications folder.
Aside from these things the app is good for what it does and if you travel a lot and use car accessible USFS and BLM campgrounds, this is a good app for $2.