43. The method of claim 28 , wherein at least one of receiving incremental input, presenting the subset of content items, receiving selection actions, analyzing the descriptive terms, determining a relationship between the content items of the first and second content systems, and selecting and ordering the collection of content items is performed on a server system remote from the users.
28. A user-interface method of selecting and presenting to a first user a collection of content items of a first content system in which the presentation is ordered at least in part based on content preferences of a second user learned from the second user selecting content of a second content system, the method comprising: receiving incremental input entered by the second user for incrementally identifying desired content items of the second content system, each content item having at least one associated descriptive term to describe the content item; in response to the incremental input entered by the second user, presenting a subset of content items of the second content system; receiving selection actions of content items of the subset from the second user; determining a user preference signature by analyzing the descriptive terms of the selected content items to learn the content preferences of the second user for the content of the second content system; determining a relationship between the content items of the first content system and the content items of the second content system, the relationship defining which learned user content preferences of the user preference signature are relevant to the content items of the first content system; and in response to receiving subsequent incremental input entered by the first user for incrementally identifying desired content items of the first content system, selecting and ordering a collection of content items of the first content system based on the learned content preferences of the second user determined to be relevant to the content items of the first content system.