Power Gift is a reverse auction site.
It features stuff like restaurant meals and online store items and works like a reverse auction. Each time someone ‘shares’ an item on their Facebook page, it goes down in price (by a random amount – between $0.01 and $2.00). The more people share something, the cheaper it becomes, first to buy wins it. It works for the users because there’s no limits to how cheap something becomes and it works for a business because they give away just one item, but if it goes ‘viral’ they get plenty of exposure.
That’s quite a novel business model. You can login to the site via Facebook.
I’ve just shared an auction for two one metre pizzas 🙂