Have I mentioned before how much I love what people are doing with Google Maps?
The BBC site Dimensions is a great use of Google Map technology. It allows you to superimpose the outlines of different cities, structures, and locations of major events in history over a present day Google map. In the example above I put the walls of Constantinople circa 340 c.e. next to Gibson City!
One thing to be aware of when using this site is that you will need to adjust the location you enter based on which outline you are wanting to view. Something smaller like the city of Constantinople can be attached to Gibson City's zip code. If you want to do something larger like the moon (yes you can do the moon) you may want to type in something like "North America"
As always let me know of any specific uses you find for this tool in the classroom!