Open Calais is an initiative from Thomson Reuters that help people in structuring unstructured data. Open Calais uses Natural Language Processing(NLP) and machine learning algorithms to analyse unstructured text to generate semantic data in RDF format.
It’s quite easy for webmasters to implement it. All you have to do is feed unstructured data into Open Calais using API’s and generate tags for people, places, companies, facts, and events in your content to increase its value, accessibility and interoperability.
Open Calais offers Free as well as Paid plans.
Update : Open Calais is now a part of Refinitiv Product Suite. Details Available Here