K introduced me to a cool Google Maps mashup yesterday: Walkscore.com
The idea is that you enter your home's address (or a prospective future home's address) and it figures out how many shops, libraries, parks, cafes, etc. are within walking distance. The end result is a score out of 100, and a nice map showing all the local amenities.
For example, my house gets a paltry 8/100 (not surprising since it's in the middle of a suburb on the east side of Seattle). Work gets a more respectable 34/100, and a friend's house in downtown Kirkland got an amaxing 97/100!
It's also useful just to find "interesting" places around an address - something Google Maps doesn't do very well on it's own.