I don’t have AutoCad, so I can’t try this out, but KML Tools Pro has AutoCad DVB macros that let you select features in AutoCad and convert them to Google Earth’s KML format; similarly, another macro will let you import a KML file into AutoCAD. From the website:
From AutoCad to Google Earth:
- select objects and create .kml file
- export points, lines, text, polygons (beta)
- apply the icon of your choice
- select zoom level that objects are visible
- output automatically layer colors
- adjust weight and transparency of objects
From Google Earth to AutoCad:
- digitize points, lines, polygons in GEarth
- save “.kml”
- import in AutoCad using wanted projection
Supported projections:
- NAD-83′ State Plane (*Alaska Zone 1 not supported)
- UTM zones
- HATT
- Greek Grid (EGSA 87)
The current download site is in Greek, but the link to the downloadable file is obvious at the bottom. An older version of the page used to be available at this link, but isn’t currently working; you might try the cached version of the page from Google.
For converting KML files to DXF format, you can also try this online converter.