Check out:
http://www.wwincrediblerewards.com
Basically, you cut the UPC codes off of the Weight Watchers products that you buy (Progresso Light soups, WW ice creams, dairy, candies, muffins, snack cakes, or any of the products that you can buy at WW meetings) and when you register here, you can send them in for rewards points.
If you are buying the products anyway, you might as well get something back out of them!
Pampers diapers used to have a similar program, and I got a big Duplo Lego set for my toddler son.
They are NOT good on the red box frozen entrees, however.