Night Earth is a web page that I created last year using the Google Maps API. In this web I have added to the Google Maps interface an additional imagery layer (copyright from NASA) that shows how Earth looks from space, and where you can appreciate the existing light pollution in many places on Earth, specially in the most populated ones.
After having converted the projection of the NASA original image in the proyection type that Google Maps uses, it is possible to switch between the normal Google Maps imagery and the night NASA imagery. Unluckly, these night images doesn't have a resolution as high as the day images used in Google Maps.
Some time later I added the option to upload your own night pictures, but not thinking in the environmental aspect, but focused towards photography, which is other of my hobbies. These spots can be hidden pressing the "hide markers" button.
I think this link could be interesting to any slashdot readers.