I am pretty happy with my cheap little Ikea foam mattress -- it 'inflates', like Duggeh said his did. I don't like this memory-foam shit, but only because I would never get out of bed ever again -- way too enticing and comfortable. I also really like -- for sleeping -- a firm mattress -- the most comfortable I ever slept was one of those exercise mats over a concrete floor -- just enough cushion to prevent the contact points from getting sore, but no more. If this sounds appealing, then I can look up which one it is, but really you should just go to Ikea and try them out, they have a wide variety of mattresses there, and a nice little lookup table to immediately tell you if it's something you'll like or not.