SteveM(PA)
Poser
A fellow in my small town (I think he's a member of the historical society) just did one of those "Then and Now" books. It would pretty much involve getting access to a photo archive of old buildings, then going out to shoot the site as it looks today. Apparently Buster Keaton used to perform at a vaudeville house (that is now an apartment building) just a few blocks away.
http://www.amazon.com/Spring-City-Royersford-Then-Now/dp/0738549274/ref=sr_1_1/103-8145533-2223825?ie=UTF8&s=books&qid=1187882135&sr=8-1
http://www.amazon.com/Spring-City-Royersford-Then-Now/dp/0738549274/ref=sr_1_1/103-8145533-2223825?ie=UTF8&s=books&qid=1187882135&sr=8-1