The name says it all -- foam! In addition to futons (and minimal futon furniture) they make all kinds of chair cushions,pillows, etc. Be sure and go down into the basement where you can watch them cut pieces from huge sheets of the stuff. Choice of upholstery fabrics is somewhat limited, but when it comes to the foam itself, you will find exactly the thickness and density you're looking for. And if you need stuffing, you can buy a bag of chopped foam here, which is so much better than that polyester batting that they sell in fabric stores. Not as cheap as the name implies, but still pretty reasonable.
more