Clustify

Clustify is document clustering software produced by Hot Neuron LLC, an 
information retrieval software and services company that has been in 
business since 2000.
 
Clustify offers both conceptual clustering and near-duplicate detection. 
  It groups related documents into clusters and labels each cluster with 
a few keywords to tell what the cluster is about, providing an overview 
of the document set and making it easy to find relevant documents during 
review.  Entire clusters and groups of clusters can be tagged with a 
single mouse click, making review faster and more consistent since 
related documents are reviewed together.  Clustify has an automatic 
categorization tool that minimizes manual labor when new documents are 
added to a case.  Clustify can handle millions of documents on a typical 
desktop computer.