As reported on Laughing Squid SepiaTown is “A Collaborative Urban Time Machine”

SepiaTown lets you use your computer or mobile device to see what the very spot you’re standing on looked like decades or centuries ago.

A Google Maps mash-up, SepiaTown allows users to upload and geotag vintage photos of urban landscapes and then serves them up for others to view.  There’s even a “then/now” feature that juxtaposes the old shot with the current Street View: