Quick, what is your House of Representatives district? Many people don't know this number, or the member who represents them. The New York Times' new Districts API makes it easy for your application to answer the question for any point within New York City, though it could serve as a template for a nationwide--or even international--service.
The previously popular Google Earth API is being deprecated and is due to shut down in early 2016, signalling the end of access to its 3D imagery via the API. This post by Timothy Whitehead for Google Earth Blog looks at four applications that used to use the API, and what they are using now.