I just love the Mac's Widgets. Is that flight tracker a new one?
Flight Tracker comes with Tiger. It was one of the first truly useful Widgets, especially for business travellers. Another was the one that helped you shop for the best local gas prices but that one was an add-on, not part of Tiger.
Flight Tracker has been around for at least a year. I've used it to determine the status of a flight a friend was flying on... told me they were 22 minutes ahead of schedule so I arrived at the airport and saved him waiting time.
My favorite is the envelope printer. All word processors have some sort of envelope function, but none of them works as well as the envelope widget. It integrates with Address Book and it prints the USPS bar code. Your snailmail looks official and gets there faster.