Making a memory foam mattress

We bought a medium density 4" foam slab from JC Penny's online, of all places, for about $50. We then added 2" of memory foam on top. Cheap, easy, and very comfortable. I've also noticed that K-Mart sells very inexpensive 6" foam mattresses of any size in a box. Should do you fine for 30 nights a year. One big advantage of an all-foam mattress is that when your sleep partner moves, your side stays stable, and you don't feel it.