From here: http://libraryhack.org/ideas/
This idea is called "This Place in History", which let user check the photos taken near them, and even the old map of that area (if available). It can be used for either a mobile app or a web site, but mobile apps for devices like iPhone, iPad, or Android phones/pads are preferred, due to the nature of the touch-based gestures and the ability to determine user's current location.
To use this app, the user firstly agrees it to use his current location, and a map will be displayed based on this location. User is able to use either gesture or buttons/scrollbars to navigate and zoom in/out. There's a long bar called "timeline", which has 2 points on it, one is "starting year" and the other is "ending year". By selecting these 2 points, photos captured between these 2 years will be shown as thumbnails on the map based on the place they've been taken, and user can click them to see the full picture and related information like author, description, date, etc. User can save the picture, share them on facebook, twitter, or by email. User can also navigate to previous / next pictures, sorting by either time or distance.
If the old map of the current displayed place is available, there will be a scroll bar to let the map face into the past map, or the present map (that is, map or satellite image or hybrid mode). Alpha transparent effect can be used so that the old and current maps can be mixed together, with proper visual effect.
I understand that some old photos may not have geodetic information. In this case, keywords can be used to determine their positions. About map, or geodetic info is not available, additional efforts will be needed to implement the features described above.
Social networking can also be added, like making friends with people who are near you and are interested in the same history time / places / photos. People can leave comments on a certain photo. Of course, this will make things much more complex and may not be provided in the first release of the app.