Here's an oldie but a goodie if you're a Simpsons fan. It's an interactive map of Springfield, the fictional home of The Simpsons that has been painstakingly recreated based on various appearances throughout the show's 19 seasons.
The map was drawn using locations that were featured on the show, as long as they appeared more than once. Some of the spacing was determined using recent aerial shots (there's a listing here).
The map was started in 2001 by Jerry Lema and Terry Hogan. The current version is about four years old (so there are no marks from the dome featured in the recent film). In addition to a quadrant view, designer Adrian Noterdaem has put together a slick Flash-based version that lets you zoom in and out. There's also a PDF and printed version of the map residing in Harvard's map collection.
I'm still waiting for the Google Earth layer.