http://www.blender.org/api/blender_python_api_current/ As of 10/11 november 2015 we can now link to the current api docs and not be worr...
August 22, 2011
matrix_world
This multiplies the coordinates as found in the object data with the world matrix of that object. Essentially giving the world coordinate of any selected vertex, even when the object origin is not at the world origin.
