quintura

IMHO quintura is on the right track. Based on your search terms the search engine renders a word map very much like the cover from the German translation of Deleuze's and Guattari's ''Capitalisme.

What I like about it: It's very intuitive and it's implemented without using plugins (Java or Flash) just making heavy use of some javascript framework (had no time yet to find out which). I'd like to have a interface like that for my del.icio.us tags.