Did you try Mooter? Mooter is a web search that shows the results in groups, subcategories and the site relations among the results. Very cool.
Mooter, an innovative search engine that also employs clustering techniques, provides researchers with several additional advantages by presenting its clusters visually. It arrays the subcategory buttons around a central button representing all the results, like the spokes of a wheel. Clicking on a cluster button retrieves lists of relevant links and new, associated clusters. Mooter remembers the chosen clusters. By clicking on the ” refine” option, which combines previously retrieved search clusters with the current query, a user can obtain even more precise results.
(Thanks for the link Renato!)