We've now got a few more tricks that you can do with KML on Maps:
- View entire photo sets as self-contained KMZ files, as exported by Picasa. We were going to write up how it's done, but Brian's blog post pretty much covers it. Check out his geo-tagged photos of Mallory Cave.
- View KML Overlays. Add your own imagery directly on top of Maps. For example, take the GroundOverlay example from the official KML tutorial and just throw the photo of Mt. Etna onto Google Maps.
- Use your own customized marker icons.
To view a KML or KMZ file on Maps, just go to Google Maps, and instead of searching for a geographical address like 1600 Amphitheatre Parkway, 94043, search for a complete Web address (including the "http://" part) of your KMZ file, like http://kml.lover.googlepages.com/cropcircles.kmz. Need your own web space to upload some files? Try Google Page Creator.
The Maps API blog has further details.