Chris O’Sullivan writes:

Thought you might like to know that I’ve created a quick little app that lets you view KML on a google map without having to save it to a file first. Check it out here, and details about it in my blog here.

It sure works for me — no more having to upload the KML file to a server first when wondering what it would look like in Google Maps. Just make sure to zoom in manually on the map to the region you’ve got KML for.