Google has released a demo app named Au-to-do to show the capabilities of their APIs.
Au-to-do is a ticket tracking service that you can implement using the Google App Engine in your own organization.
Google developers said:
A platform is more than the sum of its component parts. You can read about it or hear about it, but to really learn what makes up a platform you have to try it out for yourself, play with the parts, and discover what you can build.
With that in mind, we started a project called Au-to-do: a full sample application implementing a ticket tracker, built using Google APIs, that developers can download and dissect.