I've used a number of penny auction sites, including zbiddy. The model works like this: You buy a bid pack, then bid on the product you want. If you're the last person to bid, you win the item. The reason you get a discount is because other people are bidding too, so multiple people are investing in the product. There's some strategy to it, but that's what makes it fun. If you're willing to be patient and learn the ropes, sites like zbiddy can really pay off. I've won several auctions and paid significantly less than retail each time.