Take a look at MapCruncher. A very interesting new map mashup technique from the folks at Microsoft Research. It basically allows you to overlay any digital map image on top of a normal, zoomable Virtual Earth map.
When you gotta go, you gotta know: where’s the nearest toilet? SitOrSquat has been helping answer that question for several years. Now the SitOrSquat API will allow you to interface with the app's extensive database of public restrooms, replete with all kinds of meta data.