Geography iPhone Apps

I have to admit that I'm completely addicted to Foursquare, the mobile app that allows a user to "check in" to various locales for fun (and points and badges, of course). It feels like a geographer's version of a clue hunt. However, besides Foursquare, there are actual geographical iPhone apps that are perfect for those who love geography. With that in mind, don't miss my brand-new list of essential geography apps for the iPhone!  Did I miss your favorite? Share it here!