1. A non-transitory computer-readable medium embodying a program executable in at least one computing device, wherein, when executed, the program causes the at least one computing device to at least: generate a user interface to facilitate creation of a plurality of user-created item lists via a plurality of client devices; receive the plurality of user-created item lists from the plurality of client devices via the user interface rendered on the plurality of client devices; maintain the plurality of user-created item lists in an item list registry, individual user-created item lists of the plurality of user-created item lists including a plurality of items available for purchase, lease, or download via an electronic commerce system, and the individual user-created item lists being identified by a respective item list title that includes a title term; for the individual user-created item lists, compare the title term with a plurality of predefined keywords; for the individual user-created item lists, assign a keyword tag associated with a respective predefined keyword of the plurality of predefined keywords to individual items of the plurality of items included in a respective user-created item list of the plurality of user-created item lists in response to the respective predefined keyword matching the title term; create an item category associated with the respective predefined keyword; and populate the item category with at least one of the plurality of items when a number of keyword tags corresponding to the respective predefined keyword and assigned to the at least one of the plurality of items reaches a predefined category threshold.