We took your recommendation and stayed at Crooked Creek Campground for 3 nights while we visited the Black Hills of South Dakota. It is a centrally located camp which lends itself nicely for taking day trips throughout the Black Hills. Our cost was $77 for the 3 nights using our Good Sam Discount. The camp is located on the Michelson Bike Trail which would be great for the bicyclists among us. We used the trail for taking a daily walk. It was a beautiful trail.
The one inconvenience of this campground is its back-in dump station. We've never seen one quite like this. The dump station was not too difficult to back into, but it certainly wasn't as easy as the usual drive thru dump stations.
http://www.crookedcreeksd.com/wel.htm