There are quite a few sites out there that show historical photos or videos, along with their location on a map — you’re able to see what a particular street looked like fifty or one hundred years ago.
Here are my choices for The Best Historical Photo + Video Based Map Sites:
Historypin is probably the biggest site on the Web.
Old S.F. shows photos from San Francisco.
Time Shutter does the same for San Francisco.
What Was There lets you search for any place in the world and then shows you images of “what was there” a long time ago using a Google Maps street view. You can upload photos, too.
As always, feedback is welcome.