See What It Means with Starlight.

Example Cluster Map exported from Starlight

Starlight automatically groups documents with similar content into groups, providing a 'table of contents' for the set of documents. The individual documents can be color coded according to any property in the document. The example above shows a clustering of 1800 news articles found by Zoogma on the topic of Nanotechnology colored by the source they came from. As you can see the source colored in brown provides more "news" focused information than the others. The user can zoom in and see more details about the words used to create each cluster.