Three years ago we showed you the very useful visualization that the city of Douglasville, Georgia created to show how new road construction would be laid out. It was a great use of Google Earth and made it very easy for people to see how things would be situated.
The folks at Site3D are doing similar work, taking drawing layers and overlaying them on Google Earth. Even better, their various drawing layers are imported as individual Google Earth layers so that you can toggle off individual layers as needed.
They also support taking Google Earth paths via KML and importing them back into the Site3D software.