Not a website but I use Trailer Life Campground Directory Navigator as my main tool for planning a trip. Plan my route and I can see what campgrounds are along my route and easily add them as stop-overs. Other websites are AAA, Goodsam, Loves, Bings maps, Flying J, mapQuest, Roadside America, Google and
www.sportsmanatlas.com. all of which I use as needed.