It is true that many campground were full of FEMA trailers. However, some of the campgrounds are slowly regaining there identity again. The Hollywood Casino Campground (formely Casino Magic) in Bay St. Louis, MS, is up and running and getting rave reviews. I spoke with the MS State Park Department in Jackson, MS about Buccaneer State Park in Waveland (which was wiped out, except the wave pool) and I was told that perhaps by the end of this year, 2006, it would be back up and running. It probably was the crown jewel of the MS State Parks (campground) and also had an extremely nice water park. The wave pool survived with very minor damage and will be refurbished. The water slides are nowhere to be found.
The coast is trying to come back, and is making pretty good stides here and there, where the infrastructure is available and repaired (water and sewer lines).
Call around. And call the Mississippi Gulf Coast Tourism Commission, too. (228) 575-4297. And check out their website