The Google Earth Extension for AutoCAD is a very usefull tool. It allows you to import a Google Earth image into AutoCAD, publish your 3D model to Google Earth, drape a Google Earth image onto a 3D mesh in AutoCAD, and attach time span information to your model.
The user guide provides easy to follow steps for importing a Google Earth image into AutoCAD, publishing 3D model to Google Earth.
For those who have upgraded to the Autocad 2010 family, you can download bellow the updated utility .
Google Earth Extension for Autocad 2010.
The Google Earth Extension download contains installers for AutoCAD 2007, 2008, 2009, and 2010 in one zip file. Download, unzip, and execute the installer that matches your version of AutoCAD.