This question of 'how to clean a pillow' was recently posted to Martha Stewart at The Toronto Star.
Q. Can I clean store-bought pillows in the washing machine?
A. Whether made of natural fibres (such as down) or synthetic materials (often polyester), most pillows can be washed in the machine. They should be cleaned every three to six months to remove mould, bacteria and odours. Read instructions on the tag to make sure the pillow is not dry clean only.
It's best to use a front-loading washer, since pillows tend to float and stay dry in spots in a top-loading machine. If you don't have such an appliance, consider going to a self-service laundry. Set the machine on its gentlest cycle, using warm water. Add a small amount of liquid soap (powder detergent may leave a residue), and then fill loosely with your pillows. Repeat the rinse cycle a second time to remove soap completely.
If the tags say the pillows can be dried, place them in the dryer along with a couple of clean canvas tennis shoes or tennis balls to break up any clumps of filling. Use a low heat setting, and allow a few hours for the pillows to dry. Between cycles, take them out to fluff. For pillows that shouldn't go in the dryer (usually the foam kind), dry them on a rack or a clothesline.