Just wanted to highlight a post from the Maps API blog regarding updated KML support in Google Maps:
We've now got a few more tricks that you can do with KML on Maps:

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.