Google Earth

If you've got Broadband and a half hour to spare you have to give this a try. (Have to download it and install, but it doesn't take too long).
Basically you can zoom in anywhere in the world. Try typing your postcode in as a starting point and you'll get the idea. The maps of the UK aren't that good when you zoom right in, but try clicking on some of the major landmarks down the left handside to be REALLY impressed, - the Eiffel Tower for instance.
At first I thought this just to be another of them things that impresses I.T. geeks, but it seems I was wrong......