Google Maps API Official Blog: KML and GeoRSS Support Added to the Google Maps API
… we now support GeoRSS as a data format for geographic content in Google Maps. We want to enable users to create data in whatever format is most convenient for them, and feel that by supporting both KML and GeoRSS we can enable a wider variety of people and applications to contribute content to Google Maps. We’ve built support for the Simple, GML, and W3C Geo encodings of GeoRSS — all you have to do is enter the full URL of a GeoRSS file into the Maps query box to load the file. For example, take a look at SlashGeo’s GeoRSS on Google Maps.