App Of The Day
The Museum of London has launched a free iPhone app which brings its extensive art and photographic collections as well as geo tagging and Google Maps to guide users around London where, via the iPhone screen, various historical images of the city appear - just like in the image above. You can look into the past of the London, and explore the hidden history of London that surrounds you. This idea may have been inspired by the Flickr group, Looking into the Past.
You can download it from iTunes here.