Just a few links to some graph drawing resources I bumped into while I was looking into modifying ROCircleLayout.

http://stackoverflow.com/questions/713701/force-directed-layout-in-c

http://www.cs.brown.edu/~rt/gdhandbook/chapters/force-directed.pdf
(http://www.cs.brown.edu/~rt/gdhandbook)

http://www.cs.brown.edu/~rt/gdhandbook/chapters/circular.pdf