I'm not sure exactly what to make of this yet, but it seems interesting to me. It seems to be roughly showing how scientists working in one area move their investigations to other disciplines when researching a topic. It's interesting, but I'm not sure how useful it is. I don't detect any directionality from the graph or any sense of proportion.

http://www.lanl.gov/news/index.php/fuseaction/home.story/story_id/15960


Here's the actual map: http://www.lanl.gov/news/albums/science/PLOSMapOfScience.jpg

With this description:
"Colors represent the scientific discipline of each journal, based on disciplines classified by the Getty Research Institute's Art and Architecture Thesaurus, while lines reflect the navigation of users from one journal to another when interacting with scholarly web portals. "