SEASR's OpenNLP Entities to Protovis Network Graph is a free tool for extracting entities within a specified sentence distance within a text. The OpenNLP system is used for entity extraction, and their relationships are represented in a link node network graph generated in Protovis.
While SEASR is still active, their page for OpenNLP Entities to Protivis Network Graph is no longer available. It can still be viewed via the Internet Archive.
Comments
The website is no available but it can be seen from way back machine
https://web.archive.org/web/20121028053622/http://seasr.org/documentation/example-flows/stanford-entities-to-protovis-network-graph/