This is the single coolest thing I have seen on the web in a very long time. Real time (mostly, see below) graphic flight data from damn near every airplane in the air right now, with no Flash or Java in sight. This is, quite frankly, brilliant. For extra time-suck fun, you can click on any individual flight to get a detailed information breakout.
The web version is free (with some unobtrusive ads) and there are paid versions for all of the surviving players in the mobile market – iOS, Android, and Windows Mobile – as well as a paid ad-free upgrade for the browser version and a native app for OS X.
Interesting aside: There are two kinds of flight representations – yellow icons which are being fed from actual real-time ABS broadcast data, and orange icons which are coming from the FAA databases in the U.S. and are on a five-minute delay. While flights in European and Asian airspace seem to uniformly offering real-time data, only a handful of flights in North American skies can say the same. Weird.