How to load ArcGIS vector files into Google Earth or covert Google kml files to shapefiles.

Solutions:

1. Purchase an advanced license for Google Earth and use the "Data Import" feature;
    
2. Use stand-alone Freeware (I particularly like what's available at Zonum Solutions) to convert shapefiles to KML format and vice-versa.
   
3. Use extensions, tools or scripts that run within ArcGIS:
   1. For converting to KML: The ArcGIS 9.3 ArcToolbox contains a "To KML" utility in the "Conversion Tools" toolbox.
   2. An even better ArcScript (AS14988.zip) can be downloaded from the ESRI web.  This installs as an extension in ArcMap and has many nice features for exporting shapefiles to KML.  It was developed by the City of Portland Bureau of Planning.
   3. To go the other way, KML to shapefile, try the toolbox tool that can be downloaded as an ArcScript (AS15603.zip) from the ESRI web.