Carrot2 is an Open Source Search Results Clustering Engine. It can automatically organize small collections of documents, e.g. search results, into thematic categories.
Apart from two specialized document clustering algorithms, Carrot2 offers ready-to-use components for fetching search results from various sources including YahooAPI, GoogleAPI, MSN Live API, eTools Meta Search, Lucene, SOLR, Google Desktop and more.
Carrot2 is implemented in Java, but it easily integrates with non-Java software, such as PHP, Ruby or C#. The downloads page will help you to choose the right package.
Carrot2 is available under BSD License.
Live Demo: test Carrot2 using popular search engines
Carrot2 Website: read more about Carrot2 algorithms
Downloads: download Carrot2 binaries
Documentation: Carrot2 User and Developer manual
Issue tracker: Carrot2 bug database powered by Atlassian JIRA
Build server: Carrot2 build server powered by Atlassian Bamboo