Here are some of the links we use to find campgrounds (if you have a favorite site please let me know and I will add it):

Membership sites:

http://overnightrvparking.com/

For $25 a year you have access to nationwide free and low cost camping locations (Forest Service, municipal, rest areas, Walmarts, etc.).  Great site to find small, out of the way campgrounds. Subscribe and give referral credit to roamin_on@rvroamin.com and receive an extra FREE month!

http://passportamerica.com/

For less than $50 a year you have access to thousands of commercial campground offering 50% off to club members.  There are many restrictions but for short overnight stays this has worked great for us.

 

Government campgrounds:

http://www.militarycampgrounds.us/

For retired military and DOD personnel and provides a listing of all military campgrounds in the US.

http://corpslakes.usace.army.mil/visitors/

The US Army Corps of Engineers has many facilities throughout the lower 48.  There website has a comprehensive listing of all their facilities.  Please be aware that many of the facilities have been turned over to state or local governments.  Most of these DO NOT honor the Senior/Golden Age pass or Access pass.  Those facilities still managed by the Corps (that still honor the passes) are noted with the Corps symbol in the listings.

http://www.blm.gov/wo/st/en.html

Provides a comprehensive listing of the Bureau of Land Management (BLM) facilities.

http://www.forestcamping.com/

A comprehensive listing of all the Forest Service campgrounds put together by Fred and Suzi Dow.  They have made it a lifetime goal to visit each and every one of the campgrounds documented on their website!

 

 

The following all provide state by state listing with reviews and rates from other campers:

http://www.rvparkreviews.com/

 

http://www.freecampgrounds.com/

 

http://www.rvparky.com/

 

http://www.campgroundviews.com/

 

 

Often I will find a discount park through http://passportamerica.com/ and then check http://www.rvparkreviews.com/ to get other campers thoughts on that park before committing to a reservation or even a stop.