Bring up Google Maps and press the Street View button along the top. You should see camera icons on the US map. Those mark where the new coverage is available. When you zoom in on a marked area, the covered streets will be outlined in blue.
Amazon's A9 site tried a version of this a few years ago, but they dropped it a while back. A9 drove a GPS-equipped van with cameras on the roof up and down streets. So you could look up a shop or restaurant and see what it should like when you get there. However, it lacked the cool panning and zooming that Google's implementation has.
Microsoft is in the game, also. Their Live Search offers low-altitude, oblique aerial photography for select areas.
Thank you.