I read a fascinating article a few months ago about the growing popularity of -- get this --
laundry detergent -- as a form of "money" in many urban areas. The point of the article was that this type of commodity has become a medium of exchange because it is readily available in any grocery store or bodega, has a strong latent demand that cuts across income and cultural lines, and has a relatively high cash value on a unit weight basis (compare the cost of a gallon of laundry detergent to a gallon of almost any other product that is sold in liquid form).
Go figure.