A search engine with a recommender system. Does spelling checks for a 'did you mean' type thing -- try putting in a transposed letters. Also demos recommender system based on circ data or subject analysis. They call these boost factors. Boosting is based on content ranking, circulation, holdings strength.  The project page is at http://www.cdlib.org/inside/projects/melvyl_recommender/ .

CollaborativeRank is an attempt at building a search engine for del.icio.us that returns helpful/timely search results. The central idea behind CollaborativeRank is to motivate people to provide helpful/timely URLs by rewarding them for doing so. Currently, the rewards are as follows:

• greater influence on search rankings for a given query
• a higher ranking as an expert for a given query
• a higher ranking overall among all contributors

I believe that these rewards would give people the feeling that they are having some influence over the URLs that others visit. I suspect that many people would feel a sense of satisfaction from influencing others in this way.