Those of you that travel know how often flight schedules can be changed and believe it or not, the airport monitors aren't always up to date since those tend to be controlled by the airport and not the airlines. I fly Continental quite a bit and they have a decent page for mobile devices on their site, which will automatically recognize Windows Mobile devices and format accordingly. However, to see what all airlines are doing, at least in the US and perhaps North America, you'll need another site.
I found Flight Stats earlier this week and book marked it on my device. Just go to http://mobile.flightstats.com and the above screen will appear. In addition to flight status, they have departures and arrivals by airport, which shows all flights inbound or outbound in a given timeframe and their schedule. What is cool is, if you trace this to the gate you are waiting at, you can track the inbound flight you are waiting on and see if it has actually left, something checking on your current flight won't do. Usually it will just say "Waiting on inbound aircraft." I had a flight so delayed on Wednesday that I arrived at the airport a bit early on purpose to catch up on emails and have a relaxing dinner. I actually tracked the two preceding flights, each about an hour and a half long, and knew exactly where my aircraft was as it made its way to my gate!
As you can tell by the screen shot above, there are many other useful features, such as security wait times by airport and security line, weather reports and more. If you use something else to track your flights, what do you use?