Google bought this company for some reason, but it's very cool. Basically, it's satellite images of the entire world. For many large cities it goes right down to a level where you can see individual cars. Here's an interesting comment from one user:
The pictures of Toronto were taken around spring - summer 2002 - I know because that's the year we put in the red cedar chips in the front yard (and boy don't they show up well in a satellite photo), and my truck is parked in front of the house. We moved out in late August that year.I spent hours looking at Montreal (where I lived when I was young) and São Paulo (where I'm working during the week). I don't really know where I am in São Paulo, but I know that I'm close to a river, plus I'm working at an upper floor in a tall building (Torre Norte) so I can look down for features. In a few minutes I was able to find my building. Here's the contents of the .kml file that keyhole generated:
posted by Dipsomaniac at 7:36 PM PST on November 21 [via Metafilter]
There's a 7 day trial for this program to play with. Explore some cities you know, it's fun. Learn some geography. Recommended.