The Photoshop team, especially engineer John Penn, do a lot of work with the National Center for Missing and Exploited Children. I visited there once & was fascinated by their process. Artists use various tools (especially Liquify) to combine photos of a missing child with images of a similar kid who was the appropriate number of years older, drawn from a huge collection of donated school photos.
Now new technology from a team at the University of Washington for Illumination-Aware Age Progression seems like it could be a great aid to that kind of work:
[Via Eunyoung Kim]