Good Sam offers discounts, insurance, mail forwarding services, rallies, etc. The Escapees have their own RV parks, offer discounts, mail services, and rallies. FMCA is an excellent club for motor home owners. Visit your libraries and bookstores for books on areas of interest. The department of tourism can give you information for regional and state parks.
Counties often have nice parks.
Send for information from the National Park Service, the National Forest Service, the US Army Corps of Engineers, and the Bureau of Land Management. RV accessory stores such as Camping World often have books and magazines. Here you can find RVer's friend - a list of truck stops and the amenities to be found there. Don't forget state welcome centers. These will often give you a map and tour books free for the asking.