Another +1 for FlightTrack Pro.

I've been using it for awhile and it is awesome. It often updates the gates (even the random changes) even before the airport announces the gate change. The ability to search for flights with the same route has been a lifesaver. I've been able to catch flights on standby that I find by myself and even weigh different flight options the day of.

I just created a TripIt account that I link up with a dummy GMail account to automatically sync all my work trips to TripIt and then FlightTrack. This program is legit.