Google is officially launching Mapplets today. These are effectively widgets that can be added to Google maps – some are created by Google but there is also an API for third parties to produce their own. See Brady Forest’s post from May when Google first launched a preview of the service.
The screen shot shows the crop circles widget, which I added from the content directory. Once widgets are added, they can be seen on the beta site, which will move over to the production Google Maps when launched