Street View

Wow...Street View on Google Maps is really amazing.  It is street level photos that you can rotate 360 degrees and zoom in and out to show what you would see if you were standing on that point in the map.  So far it only exists for New York City, Denver, Miami, Las Vegas and San Francisco but hopefully this is just the beginning.  This is one of the Google Map features that I've been waiting for, (although it wasn't quite as awesome in my head... it was more about photo reference shots for directions).  If you haven't tried it out yet, go do it right now at maps.google.com and click on Street View.