Amnesty Generator is a free utility that converts any Google Gadget into a Dashboard widget. Google offers over a thousand Google Gadgets.
Using Google’s new Add to your webpage feature, select a webpage gadget, copy and paste its HTML code directly into the Amnesty Generator window, tweak some settings (if you wish) and generate a new widget with the click of a button. From there, you can install your new widgets into Apple’s Dashboard, Amnesty Widget Browser, or even convert them into a standalone OS X applications with Amnesty Singles.
More info and download link here.
Google Gadgets can be found here.