7. A system, comprising: at least one computing device; and an item categorizing service executable in the at least one computing device, wherein, when executed, the item categorizing service 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; obtain a particular item list of the plurality of user-created item lists from the item list registry; compare the title term of the particular item list with a plurality of predefined keywords; assign a keyword tag associated with a particular predefined keyword of the plurality of predefined keywords to individual items of the plurality of items included in the particular item list in response to the title term matching the particular predefined keyword; create an item category associated with the particular predefined keyword; and populate the item category associated with the particular predefined keyword with a particular item of the plurality of items based at least in part upon a number of keyword tags assigned to the particular item reaching a predefined threshold.
7. A system, comprising: at least one computing device; and an item categorizing service executable in the at least one computing device, wherein, when executed, the item categorizing service 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; obtain a particular item list of the plurality of user-created item lists from the item list registry; compare the title term of the particular item list with a plurality of predefined keywords; assign a keyword tag associated with a particular predefined keyword of the plurality of predefined keywords to individual items of the plurality of items included in the particular item list in response to the title term matching the particular predefined keyword; create an item category associated with the particular predefined keyword; and populate the item category associated with the particular predefined keyword with a particular item of the plurality of items based at least in part upon a number of keyword tags assigned to the particular item reaching a predefined threshold. 10. The system of claim 7 , wherein the particular item list is a first item list of the plurality of user-created item lists, and the title term of the first item list and the title term of a second item list of the plurality of user-created item lists both match a same predefined keyword of the plurality of predefined keywords.