For the developer seeking to experiment efficiently with social APIs, O'Reilly's 2nd Edition of "Mining the Social Web" is a truly outstanding resource.
Author Matthew A. Russell drops the developer right into the sandbox of each social network (Twitter, Facebook, LinkedIn and Google+ are particularly emphasized, as you would expect) with just the right amount of explanation about what's accessible via each dataset, and then clears out all the obstacles so they can start data mining against very clear examples.
The Google Maps API naturally has a rich history on ProgrammableWeb. Over the last year or so, Google has released additional maps-related APIs as separate services. One of the latest ones is the Google Distance Matrix API. This allows a developer to submit a matrix of locations, as origins and destinations, and get a list of the distances in return.