Beware not all COE campgrounds are ran by the COE. Here in AZ they were turned over to AZ Parks Service and there are no dicounts, full price only. If you are at a COE ran Campground, they will have a DVD that shows COE built facilities. DVD is named "Your State by State Guide, Recreation opportunities with the U.S. Army Corps of Engineers" www.CorpsLakes.us Got the DVD at a COE Campground in New Mexico.
We've been using Ultimate Campgrounds for the past couple of years and find it quite useful. It seems to have all COE locations as well as lot of others.
There is a book which lists all COE parks with camping "Camping with the Corps of Engineers" available from your favorite online book seller. Ours is the 8th Edition it is now in 10th Edition. We use it all the time each state that has COE parks and locations of them. Some states DNR's run parks at some lakes. Don't know whether that was to get state support for the lake/dam or if COE didn't want the hassle of running campgrounds.