Based on the tip at Mac OS X Hints I whipped up the following file which allows Safari to automatically open links to Google Earth files:

Code:

---

<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.comProperty-List-1.0.dtd">
<plist version="1.0">
<dict>
	<key>LSRiskCategorySafe</key>
	<dict>
		<key>LSRiskCategoryExtensions</key>
		<array>
			<string>kml</string>
			<string>kmz</string>
		</array>
	</dict>
</dict>
</plist>

---

Save this in a text file named "com.apple.DownloadAssessment.plist" in your Home > Library > Preferences folder, relaunch Safari and Google Earth links will open automatically. Also make sure that you have "Open safe files after downloading" checked in Safari's prefs.