Infonetware RealTerm Search
NO LONGER IN SERVICE AS OF 2006
This site is primarily designed to demonstrate classification technology from Infogistics. It’s a meta search engine, and it does topical classification of results. However, Infonetware RealTerm Search is unique in that you can select several different topics, then “drill down” to see results from all of them, rather than being restricted to the results from only one topic.
You will also find meta crawlers on specific niches in this category as well: http://www.mynichesearchengine.com/category/niche-search-engine/