Hi Drew,
An anaology of the Air Miles program that Blonde Bomber describes also exists in the United Kingdom
http://www.airmiles.co.uk . I would say that the majority of the redemption is for flights but you can also get leisure activities (bowling, theme parks, cinemas, discounts on cruises). They also offer 'special gifts' like balloon flights, days on a racetrack, beauty treatments, etc.
Doesn't American Express in the USA allow you to sell a number of membership reward points for cash, which can presumably be used for merchandise?