1. A method performed by a computer for providing an on-line real estate auction service and an on-line property listing service, the method comprising the steps of: registering, by the computer, a seller of a real estate property who is not represented by a third party real estate agent; receiving, by the computer, property description data items describing the real estate property; receiving by the computer a user instruction indicating that the property description data items are to be posted; posting by the computer the property description data items for viewing, responsive to the user instruction; receiving by the computer a user indication of a posting type as one of an on-line auction, an on-line property listing, and a combination of both the on-line auction and the on-line property listing; determining by the computer a type of the posting based on the user indication of the posting type; responsive to the determination of the type of the posting as an on-line auction, providing by the computer at least a portion of the property description data items in connection with an on-line auction; responsive to the determination of the type of the posting as an on-line property listing, providing by the computer at least a portion of the property description data items describing the real estate property in connection with an on-line listing service; responsive to the determination of the type of the posting as both the on-line auction and the online property listing, providing, by the computer to the at least one potential buyer, at least a portion of the property description data items describing the real estate property through both the auction service and the on-line listing service; registering, by the computer, a plurality of potential buyers of the real estate property, wherein at least one of the plurality of potential buyers is not represented by a real estate agent; and responsive to the determination of the type of the posting as the on-line auction service, the computer accepting a plurality of auction bids on the real estate property from at least a portion of the plurality of potential buyers during a predetermined period and mediating the auction to produce a selection of one of the plurality of auction bids as a winning bid.