The Panoramio web site has a great collection of photos from all over the world, and they also have a very convenient web API. I thought it would be a lot of fun to use Android to access this content while you are out walking around – and especially to have Android find interesting photos based on your current location. The resulting open source application is now available in the apps-for-android project.
The application starts by showing your current location in a custom MapView. You can pan and zoom this map to choose the area you want to search.