The SwapItShop is an online trading system that lets you trade unwanted stuff for points, which you then put towards other items on the website that strike your fancy.
The system is simple - just pick something you no longer want, post it with a photo, description, and how many point you want for it, and other people bid on it. When your item is auctioned off, you send it off to SwapItShop, and you will then have points to go towards another item on the site you do want.
It's a pretty great way to barter instead of buy, have a better selection of trade items, and to keep products in the consumer stream. But it doesn't quite beat the excitement and lower carbon footprint of taking your things to the local swap meet.
