This is getting better and better. Today Amazon's A9.com introduced Mapquest maps with ground level photos. They've already got over 20 US cities including my very own San Francisco. The yellow lines in the photo show streets with the most photos. It works interactively. Now you can explore a city remotely. And see the buildings and landmarks around where you are going which should help you find places when directions aren't quite enough. Check it out! [Yahoo!]
UPDATE: a more in-depth, 2 page piece at Wired talks about what A9 is trying to achieve, how they did the mapping and other interesting tidbits.