Darren sez, "Okay, get this: You look at a map of the United States, with each zip code represented as a single white dot. You punch in a zip code – say, your own – and watch as the applet zooms down on that specific location. For example, the entire country is white dots to begni with; then, when you hit '9', only the West Coast lights up; with '0', Los Angeles, and then '210' narrows it down to Beverly Hills in specific. It's frighteningly addictive."
(Thanks, Darren!)