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

There are already plenty of good third party widgets available. In addition to crop circles (my personal favorite, see, for example, this events widget produced by Zvents.

The widgets are served via an IFrame and can include HTML, Javascript, and Flash elements. Google also has a Javascript API.