Phillip Holmstrad has a free web app up that batch-geocodes multiple US addresses, and will even turn them into a KML file for you. (I don’t know if the KML functionality is a recent addition, but I’ve only just noticed it via this Google Earth Community posting.)
I can’t wait for the day that my address book supplies a live network link to Google Earth like that. Nor can I wait for the day that the technology exists to geocode addresses globally seamlessly. (Well, okay, I can wait, but I do so impatiently.)
[Update 19:16 UTC: Yes, Phillip confirms the KML-generating functionality is brand-spanking new, as is the ability to save the geocoded result as a URL to a map using Yahoo’s API. This map, in turn, also has a KML generation button, so in effect, you have a way of saving the KML content file online, for use anywhere.]