Google released the AJAX API Playground, which’s an interactive learning-by-doing for things like the Google Maps API, their Search API, or their Visualization API, and is currently loaded with over 170 samples for 8 Google JavaScript APIs that you can edit and run to help you explore what Google's APIs have to offer. You can select a sample of one of the various APIs from the left, view and edit the code, and then hit the Run button to see how it appears in the browser. If you log-in with your Google Account you can also save your code changes.