Clustering search engine

nbruce writes "Try the Vivisimo search. It has a clustering feature that is very nice--reminds me of what librarians try to do with cross references and referrals.

I tried "academic libraries" getting 141, with clusters referring to research libraries (26), public and academic libraries (14), various directories, associations etc. But some libraries have embedded the term so I also got specific libraries like Texas A&M and Abilene Christian."