TextWise http://www.textwise.com/ "creates the semantic Digital DNA of documents, revealing the fundamental meaning of text. Semantic Signatures® mine content to uncover the deeper meaning of text and creates a unique ’signature’ for every document it processes. Eliminate the need to find or categorize documents using ambiguous keywords or entities.
The TextWise Semantic Cloud provides a service for enterprises to retrieve real-time, highly relevant matches within their own private and secure dynamic content collections.
Using Semantic Signatures® a whole new class of search applications is possible. TextWise has created one such application — Similarity Search. Similarity Search enables fast and accurate information discovery."
Also provide the Semantic Hacker API http://www.semantichacker.com/api