It seems to be only for select cities at the moment. But you can view a virtual tour of the streets. Staying along the road, you can pan around and see the world at incremental points.
Here is a Street View Demo.
To get to it from the Google Maps default view, you will select the “Street View” in the top right of the map (similar to Map, Satellite, Traffic, or Hybrid). You will mostly likely need to be focused on a city that has this option, such as San Fransisco, New York, Denver, etc. A Camera Icon will appear of each city.
When will Google install tiny chips into our brains, or let us know they already have. Great work, Google.