With a domain like map.pr, you'd think this would be another link shortener. Instead, it uses the Foursquare API to give you a great way to visualize popular places on FourSquare. And, if you're following the World Cup, you can also use Mappr to find spots frequented by fellow fans.
About.me is a popular service that allows anyone to create a single page profile of yourself that can connect to your profiles on Facebook, Twitter and other popular services. The concept is simple but limiting to the services that it currently connects to. This is no longer the case with the release of the About.me API that now allows developers to write new applications that can integrate into the About.me profile page.