You may know about adding image overlays in Google Earth. But did you know that you can publish these overlays in Google Maps and share them with others?
Example: I took a portion of a map of the Stevens Creek Trail here in Mountain View, CA and added it as an image overlay in Google Earth. I then saved the overlay as KML (right click the overlay in the Places panel > Save As). I posted this KML file on a website. Next, I went to Google Maps, typed in the URL of the KML and clicked Search Maps. In the resulting page, I clicked Link to this page and copied the the URL. View the Steven Creek Trail in Google Maps.
Here is another example showing an image of Mount Etna.
Note that any image overlay added to the Google Earth Community boards can be viewed in Google Maps by using the link at the top of the posting.