Do you use there straight out drawing capabilities? Or is there someway/plugin which allows the drawings to have the semantics of a graph (e.g. Line routing or layout managers.
FYI I use yEd because it deals with all the semantic stuff very well.
Speaking of Google, their Doodle today celebrates the Grimm Fairy Tales. Not sure if they did that on purpose, but it sure ties in to the whole "doomsday" theme going on.