Is there a network map of subjects and how they connect with each other?
Here is a subject map of science:



It is taken from the following paper, freely available from Plos One:

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039464?imageURI=info:doi/10.1371/journal.pone.0039464.g001

I think that this is the sort of thing that you are interested in. 

N.B. I am not a co-author, nor have I read the paper, so I make no judgment on its quality.