(Updated May 30th/07: YouTube demo clip, more details..)
Google has just launched an absolutely mind-blowing new feature for Google Maps called "Street View", and it's available for the following US cities: San Francisco Bay Area, New York City, Las Vegas, Denver and Miami. Street View gives you the ability to view 360° panoramas of street-level imagery on Google Maps:
For a cool demo of how this works, take a look at this fun YouTube clip:
..This page features the same YouTube clip with more information and links to read about.
This new Maps viewing experience is much better test driven than being read about so head over to Google Maps (or follow the direct city links above), center the map on the US and click "Street View" up at the top. Choose a city with a camera marker and zoom in to have a play!