I'd like to suggest that someone work on a visualization function for Zotero. I'm thinking of something along the lines of EndNote's RefViz, which gives a visual map of clusterings of articles that share keywords. I find this very helpful for trying to get a sense of how articles in area are clustered around sets of keywords and issues; especially when you are unfamiliar with the area, this can give you a 'map' of the discipline.

One things that occurs to me: when Zotero gets to the stage of letting users share libraries, etc., the visualization could be used to get a a sort of collaborative map of how a set of users have tagged an area. I.e., the visualization might be based not on keywords in the article abstracts, but on user tags.