I have been shying away from the rash of LinkedIn graph visualizations but then I ran across this one by Whitney Hess at her Pleasure + Pain: Improving the human experience one day at a time blog.
The title alone made me take a double take.
This post merits your reading as an introduction to network analysis, albeit presented in an easy to understand way with eye-candy along the way.
While you are there, check out her archives and other posts as well.
If I could get topic map project managers to read one article, it would be that one.