My wife and I use the Good Sam online Trip Planning guide. It has been really helpful we also get our directions to the camps they have an excellent trip guide and even give you the current price of gas on the road. Another great resource is the National Park Service online. The url is:
http://www.nps.gov/ they have listings for all the parks. You can search by zip code, by geographic location (State). There is lots of information as well.
We also have the 2004 Trailer Life Directory, which has proven to be an invaluable asset.
Happy camping.
John & Yvonne Quigley