Software

ZDNet recently ranked Vivisimo tied for 1st among all websearch tools:

http://www.zdnet.com/searchiq/

Vivisimo is a text clustering product that crisply organizes search
engine results into spontaneous hierarchical categories.  In
clustering approaches, no knowledge of the larger text collection is
needed, only of the streaming search results.

Vivisimo is based on the AI conceptual clustering idea: it interleaves
the process of forming clusters and labelling them, so that the final
clusters are guaranteed to be cohesive and humanly well described.

- Raul