Open Calais Content Maps
OpenCalais is a web service that aims to enable the semantic web. You can send it any unstructured text, and it will return you a list of elements: people, countries, organizations, etc. Perhaps most interestingly, it attempts to extract relationships, which allows us to get a glimpse of more than just the top-level structure of the text.
I've built a tool in Processing which will take any text source and build a 'content map' showing these elements and relations.
This is a content map of an excerpt from James Joyce's Ulysses.