Offersdepot
http://devbox.mediavue.net/offersdepot/

This online service combine features of web store and auction. Sellers and buyers are registered there. Sellers can list their goodies under different categories, and buyers can choose products and then offer the price they agree to pay. Then, seller can negotiate back with buyer on the price, and, when agreement is achieved on the price, they can make a deal. Buyers and sellers are track their invoices. Buyers then can rate sellers on service quality.