Mappr is the location-based 'mod' to Flickr that posts pictures on a map based on location. This is a great idea. However, it requires a user include the location in the 'tags', such as city & state or zipcode in their Flickr post. A simple enough means to get the location of your Flickr photos and doesn't require users to upload pictures to yet another server. Unfortunately Mappr doesn't use latitude and longitude coordinates, and is limited to the United States.
There's no reason it has to be restricted to the US, but I guess they're doing a proof of concept first.