There is a pretty good app called window seat that can help you track your flight in almost real time. You set it right before take off and it uses the flight plan on file to help you identify your position in flight without a gps. It is pretty good and accurate if you start it at the right time and the captain doesn't stray off flight plan too much. It's also fun because it is basically like a flight map similar to the ones on international flights.

It could definitely help you narrow down your location when you see things of interest.

I have it for iPhone and iPad, not sure what other PDAs support it.