Bass River State Forest has great camping. They have cheap campsites on the water as awell as cheap leanto type rentals. Great spot if you have a canoe or kayak
There's a place on Rte 9 in S. Jersey near Tom's River or Forked River. I can't think of the name, but our friends have a trailer and camped there. Nice in the summer. The Pinelands also has some nice campgrounds.