Google has opened a new service called Street View which is a series of inter-connected 360-degree panoramas over a layer in Google Maps. Right now only a few American cities have been transformed into it but for example New York and Las Vegas have been covered well. This opens possibilities for virtual plane spotting, because you can actually "travel" to places you could use for spotting in real life. However, you can only be on a road so good views can be rare.

This is Terminal 3 at JFK and some Delta(?) planes can be seen:
http://maps.google.com/?ie=UTF8&om=1...896&spn=0.006529,0.008186&t=k&z=17

At LaGuardia, an American 767(?) taxing to runway:
http://maps.google.com/?ie=UTF8&om=1....883089&spn=0.006517,0.008186&z=17

At Las Vegas McCarran a Southwest 737 is departing:
http://maps.google.com/?ie=UTF8&om=1....159303&spn=0.006955,0.008186&z=17

Parked business jets at McCarran:
http://maps.google.com/?ie=UTF8&om=1....172306&spn=0.006954,0.008186&z=17

This is interesting because you can actually "travel" by road to the airport, going through tunnels below the runways and see black limos picking up passengers from the terminal and so on.