Indirect exchange site. You put in what you are willing to give away e.g. a CD and what you are looking for e.g. a coffee mug. The site trawls all the 'swap' sites (like Craig's list) looking for intermediate swaps that will achieve the desired result e.g. you have a CD, Tom has a tennis ball and William has a coffee mug. William wants a tennis ball and Tom wants a CD. The program matches you all up so you give your CD to Tom, Tom gives his tennis ball to William and William gives his coffee mug to you. A 'mega-barter' system like this removes the need for a currency ...