1. A user-interface method of selecting and presenting 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 the user learned from the user selecting content of a second content system, the method comprising: receiving incremental input entered by the 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 user, presenting a subset of content items of the second content system; receiving selection actions of content items of the subset from the user; analyzing the descriptive terms of the selected content items to learn the content preferences of the 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 are relevant to the content items of the first content system; and in response to receiving subsequent incremental input entered by the 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 user determined to be relevant to the content items of the first content system.