Open Sahara is a free webservice that can analyse, index and semantically enrich the content of documents, websites, and blogs.
Additionally, Open Sahara offers professional services for software development related to text-mining, indexing, kowledge extraction, semantic plugins and applications.
Cytoscape is an open source software platform for visualizing complex-networks and integrating these with any type of attribute data. A lot of plugins are available for various kinds of problem domains, including bioinformatics, social network analysis, and semantic web.