Tracking flights used to be a chore, if it could be done at all. There were routes to learn, possibly hooking into the shortwave radio to get updates and hear chatter from the tower. Mostly it was a matter of faith. Saying goodbye to someone at the gate, then waiting to hear by phone that they were at their destination. The 'net has changed all that. Today it's possible to find all kinds of flight information -- heck, you can micro-manage the entire flight from your easy chair if you want. For starters, there's everyone's favorite search engine, Google. Simply put in the airline and flight number and get back all kinds of results, most helpful is the one at top which shows the status of the flight. This is also a great tool for people rushing to the airport, as they can see if their flight's been delayed right from their cell phone. Normally this results page also prominently links to flightstats, one of the leading flight information sites where you can get more details.
Now, if you want to get all geeked-out about it, check out this list of the best flight tracking sites out there. Sure, flightstat is included, but wait--there's more. There's sites out there that let you watch a representative picture of the plane as it flys its route, some even show you the ups and downs of altitude, and even bring Google Earth into play. And oh yes, one in particular lets you listen to the live air traffic control (ATC) audio feed. Very cool indeed.