Watch people from around the world access your site. Above are the most recent visitors to FlowingData. Each circle represents a visitor, and circle size increases with number of requests by that visitor. The very first white dot is where I think you are.
Visitr makes use of Modest Maps, a display and interaction library for making your own tile-based maps, and TweenFilterLite, which makes it easy to tween your objects efficiently. Lastly, IP addresses are mapped to locations using MaxMind's GeoLite City database. GeoLite City has about a 76% accuracy on the city level for the United States. The display is implemented in Actionscript 3.0 and runs in Flash; the backend was written in PHP.