25. A system for presenting items that are complementary to an item of interest, the system comprising: a data store that stores rules data that define complementary items based at least in part on prior sales performance of the complementary items; and a computing device in communication with the data store that is operative to: generate one or more combinations of items, each combination of items including an item of interest selected by the user and one or more items that are complementary to the item of interest, each of the one or more complementary items being automatically selected in accordance with the rules data; and cause each of the one or more combinations of items to be displayed to a user as a pre-selected unit for by the user; and for each of the one or more combinations of items, cause display of a purchase control through which the user initiates a purchase of the item of interest and the one or more automatically selected complementary items pre-selected unit.
25. A system for presenting items that are complementary to an item of interest, the system comprising: a data store that stores rules data that define complementary items based at least in part on prior sales performance of the complementary items; and a computing device in communication with the data store that is operative to: generate one or more combinations of items, each combination of items including an item of interest selected by the user and one or more items that are complementary to the item of interest, each of the one or more complementary items being automatically selected in accordance with the rules data; and cause each of the one or more combinations of items to be displayed to a user as a pre-selected unit for by the user; and for each of the one or more combinations of items, cause display of a purchase control through which the user initiates a purchase of the item of interest and the one or more automatically selected complementary items pre-selected unit. 32. The system of claim 25 , wherein the rules data define an order in which the one or more combinations of items are displayed.