Great holy creeping cows! This is an example of the unexpected harvest reaped by those who invest in web services. Flickr, the oft-commented-upon photo web site, has a nice web services API (application programming interface) to talk to their site. On the strength of this, a San Francisco company called Stamen Design built something called Mappr that places Flickr photos on a map of the U.S. The result is a marvel of UI design.
Highlights: I like the slider for which the little slider “thumb” is the number you’ve selected. Also, be sure and look at the postcard project for Eric Snowdeal’s little (prematurely delivered) boy.
Mappr is a parable for our new age. When you open up your interface, riches come your way. From which direction you can never tell.
Rambles Blog at Star Chamber 
You’re right, that’s pretty cool. I am not sure exactly what it is — a new filtering method on flickr tags? — but it sure is fun.