Northwest Airline's destination map is actually really helpful. I was surprised that it was more than just a JPG, PDF or Flash version of their flights with the little semi-circle lines from one hub to another. If you click on one, it becomes your starting airport (and you can set it for the session as where all flight plans begin) and then the 2nd click is where you want to go. You can then see how many connections (if any) it would take and where the connection(s) would be (which airport, that is.)
I'm surprised, and pleasantly so, therefore I'm impressed. Nice job NWA!