from PyGeo http://pygeo.sourceforge.net/distinguishes.html
from http://www.vpython.org/contents/contributed.html
from http://compwiki.physics.utoronto.ca/Physics+with+VPython
http://query.nytimes.com/gst/fullpage.html?res=9B0DE7DD163AF930A35751C0A9619C8B63
http://www.4dsolutions.net/ocn/pygeo.html