1. A non-transitory computer-readable medium storing computer-executable contents for shipping items specified in a single customer order, the customer order further specifying a destination address, wherein when executed on a computer said contents cause the computer to perform: identifying a plurality of distribution centers that collectively have adequate inventory in the items specified in the order to satisfy the order; initiating packing, at each identified distribution center, a shipment containing a proper subset of the items of the order; selecting a carrier to deliver the packed shipments; accessing shipper performance information compiled by a party other than a selected carrier providing typical delivery durations for packages delivered by the selected carrier in each of a plurality of delivery scenarios, each delivery scenario specifying at least an origin location and a destination, the plurality of delivery scenarios for which typical delivery durations are provided including delivery scenarios all specifying the destination address specified for the order and each specifying an origin location corresponding to one of the identified distribution centers; using the accessed shipper performance information to select a release time for each of the packed shipments, such that the selected release times are expected to cause the selected carrier to deliver all of the packed shipments to the destination address at a common delivery time; and releasing each of the packed shipments to the selected carrier in accordance with the release time selected for the packed shipment.