This might be useful for tourist but might be a little scarey for locals. Google Maps has a new feature called Street View which can show you 360 degree view of a particular address (street) in color. For example if you are visiting and wonder how's the hostel you will be visiting look like or wondering how the street surrounding it look like, this might be useful to you.
http://maps.google.com/
and click on the Street View box
This feature is available for San Francisco, Denver, Las Vegas, Miami & New York.