Web Clustering

Carrot2
A search results clustering framework. Includes clustering components and a stand-alone meta search component.
http://sourceforge.net/projects/carrot2/

Dowser
Clusters results from major search engines, associates words that appear in previous searches, and keeps a local cache of all the results you click on in a searchable database. It helps keep track of what you find on the web. [Windows, UNIX, Linux and Mac OSX.]
http://dowser.sourceforge.net/

Grokker Web Clustering
Grokker clusters Google's results and local files. It uses an interface which visualizes clusters by means of circles.
http://www.grokker.com

MetaCrawler/HuskySearch/Grouper
Grouper partitioned the results into clusters, or groupings of URLs which contain similar content.
http://www.cs.washington.edu/research/projects/WebWare1/www/metacrawler/

Mooter
A metasearch clustering engine for Web, Books, News.
http://www.mooter.com/