A cool project that I recently found that holds some sentimental value to myself is 110 Stories, an app that allows the user to superimpose the World Trade Center Towers back into the skyline.
The app will first guide the user to the correct orientation so that the towers are placed accurately in the picture. One can then take a picture and write a story about whatever their heart desires. The picture and note will then be showed on an online map where you can view locations where others have taken pictures from and comment.