A System for Visualizing Bibliography Information
To elaborate a little on my comment (which is slightly tangential).

There is a fun site called eigenfactor that provides nice visualizations of how various parts of science cite each other, and their relative size by publication/citation volume. Unfortunately their primary focus seems to be calculating impact factors for journals and so they operate on the level of journals, not individual papers/authors. However, they have a pretty interesting way of identifying subfields.

They use the number of citations from a journal A to a journal B as a weight on the edge from A to B. They then consider a random walk on the resulting graph. Such a walk tends to linger in topic clusters, and thus when they try to create a shortest description of the walk they tend to name the clusters and use a second index inside the cluster (kind of how you would have unique city names, and unique street names in each city, but redundant across cities). I thought it was a pretty nice way of finding clusters, and produces clusters that mimic how most people would divide the topics in science (with the occasional hilarious classification like putting Phys. Rev. Letters in Chemistry instead of Physics) You can read more in their paper or on the mapequation site.