Here’s a short post recapping my series on free (or cheap) ways to export shapefiles to Google Earth’s KML format:
Using GPS TrackMaker to quickly export point and line shapefiles into KML format. Not a lot of flexibility, though, and limited attribute export.
Shp2KML exports point, line and polygon shapefiles, with more attribute data than GPS TrackMaker. No ability to modify KML plots based on attribute data, limiting usefulness, especially for polygons.
shp2kml uses a wizard approach to export shapefile data to KML format. Allows you to export multiple attributes, and to vary plot color depending on attribute value. Has some problems with large shapefiles.
The only paid solution here ($29.99), but by far the most flexible and powerful.
Since the first two solutions above require the shapefile to be in Google Earth’s native coordinate system (geographic coordinates, WGS84 datum), here’s a great program to convert shapefiles in virtually any coordinate system to the right one for Google Earth.