I came across this today on Flowing Data (a blog which I sometimes nod my head at, and (at times) frown and shake my head slowly).
Here is some interesting things you can do with R, a tool I learned to use during my Masters program at UVA. We never got into this kind of use, so it is a bit of an eye opener.
The flight data in the Flowingdata example follows the same method as
http://paulbutler.org/archives/visualizing-facebook-friends/ used for facebook connections.