Chris O'Sullivan has created a Rails application (Display KML on a Map) that let's you quickly test KML code directly in Google Maps. While Google Maps will display KML files, the KML file first has to be saved someplace. This method allows you to copy and paste the KML code into a text field and then display the KML information within Google Maps. You then need to zoom the map in manually to display the KML information. This is nice for testing and saves time since you don't have to first upload the KML file in order to see how it looks in Google Maps... By way of OgleEarth