Given the amount of time that we spend sleeping -- or trying to sleep -- it only makes sense to make our beds as comfortable as possible. Today, we have many choices in mattresses, from pillow-top to firm. But what happens if your mattress preferences change from day to day? Maybe an ultra-firm mattress works for you sometimes, but other times you prefer a softer bed. For changeable comfort, an air mattress just might be your best bet.

Air mattresses are equipped with inflatable, adjustable chambers. One such air mattress, the Sleep Number bed by Select Comfort, comes with two separate air chambers. A numbered remote dial controls each air chamber. The customer adjusts the mattress to the desired firmness -- or softness -- with the touch of a button. Since there are two chambers, each side of the bed can be controlled independently. This is ideal for partners with different mattress preferences.

LoungAir is offering a unique air mattress that converts to a lounge, chair, or recliner. Another type of air mattress is the low-cost, foldable variety. These inflatable mattresses are great for spare bedrooms, guest rooms, slumber parties, and even camping trips. Most of these air mattresses are simply put on the floor. These mattresses can be found at bedding stores such as Linens N Things and Bed, Bath & Beyond. They can also be found at department stores. At the time of this writing, WalMart was offering a two-position air mattress on a frame for $34. Some outdoor and camping supplies stores also sell air mattresses, as well as many online stores.

One company, however, created a more comfortable alternative to the on-the-floor air mattresses. The Raised AeroBed, by Aero Products International, Inc., is an inflatable bed that stands about two feet high. This type of air mattress can be inflated with a small electric pump.