Originally a Japanese mattress, western manufacturers have adopted the name for a significantly thicker version of its Japanese older brother.  Japanese futons are only about two inches thick and are designed to be rolled up when not in use.  Western futons, however, are typically 6-10 inches thick and are often folded up with a special futon frame to serve as a couch.

Many people like western futons because they tend to be fairly firm mattresses.  They are also inexpensive compared to other mattress types and as a result are popular with students and those on a tight budget.  Urban futon owners often cite the space-saving versatility of the bed & couch frame, particularly in cramped studio apartments.

Western futons contain many of the same materials found in innerspring mattresses including wool, cotton, foam, latex and polyester.  The main difference between a futon mattress and a "regular" (innerspring) mattress is the the lack of springs in the futon mattress and the stronger futon covering (sometimes canvas or heavy cotton). As the futon industry has grown since the sixties and seventies, many hybrid mattresses have been developed including innerspring futons, futons with memory foam, and futons with a wide variety of covers (including leather!). Even some of the major mattress manufacturers like Simmons have gotten into the futon market with their own line of Beautyrest futon mattresses.

Many of the larger mattress chains don't actually carry futon mattresses, preferring instead to guide their customers towards more high-end innerspring and foam mattresses.  However, a local Google search for futon retailers will surely turn up furniture and mattress stores selling futons.  The Futon Shop is a popular Bay Area futon chain.

Futons can be quite heavy depending on the thickness of the mattress and the sheer amount of cotton batting filling the futon. Futons constructed from a mix of foam and cotton are usually ten to twenty pounds lighter than a 100% cotton futon.  Cotton & polyester futons also weigh less than all-cotton construction but can suffer from sagging if the blend is heavily on the polyester end of the scale. A new kind of process called densified polyester has been designed to alleviate this symptom. Wool futons make up a small percentage of the futon market.  These futons offer excellent performance in terms of weight and support but don't fare so well on flexibility and price.  However, an added bonus for both polyester and wool futons is that they are flame retardant, a great safety feature.