Those other search engines

Clusty is a cluster-based search engine. You do a search and it returns results just like Google or Yahoo, however the sidebar also shows conceptual “units” that might fit your search. For example, searching for “statisitcal software” brings categories such as SPSS, Free software, and Mathematics.

IceRocket is a more mainstream search engine, but its results are fairly accurate and it includes tools for building RSS feeds of searches and adding them to popular web-based aggregators.