Eurekster
Eurekster: a social search engine.
From the material on the web site, eurekster lets members set up social networks friendster-style (though without all that personal info stuff). as you search the internet, eurekster observes which links you follow. then when your friends do similar searches, eurekster promotes links in their results that you clicked on. and vice-versa of course. The result, presumably, is a sort of community-determined idea of what links are good.