Another forum where I hang out has had some great links to what is now known as "computational rephotography."
Links at EnglishRussia.com may be NSFW for ads.
http://englishrussia.com/?p=2678 - Kiev
http://englishrussia.com/?p=2235 - Leningrad
http://www.wired.com/gadgetlab/2010/07/camera-software-lets-you-see-into-the-past/
http://www.wired.com/gadgetlab/2010/07/gallery-of-rephotography-shows-wwii-in-todays-cities/
http://www.good.is/post/ghostly-photos-of-occupied-amsterdam-mashed-up-with-modern-amsterdam/
http://www.flickr.com/photos/hab3045/sets/72157600208168658
Links at EnglishRussia.com may be NSFW for ads.
http://englishrussia.com/?p=2678 - Kiev
http://englishrussia.com/?p=2235 - Leningrad
http://www.wired.com/gadgetlab/2010/07/camera-software-lets-you-see-into-the-past/
http://www.wired.com/gadgetlab/2010/07/gallery-of-rephotography-shows-wwii-in-todays-cities/
http://www.good.is/post/ghostly-photos-of-occupied-amsterdam-mashed-up-with-modern-amsterdam/
http://www.flickr.com/photos/hab3045/sets/72157600208168658