Thanks Bob.
There's only been a couple that i've seen, one being at Computer Arts, and that one was just a basic photo-merge effect -- masking out an old lady photo in specific areas to reveal the younger lady photo beneath. I don't really consider that a viable solution to this effect. But that may just be me.
For an effect like this... the Liquify, Smudge, & Clone tools are your best friends. The hardest thing to do is know how a person's face might age. Being able to "visualize" that is tougher than making the transformation happen. You'll need to study photos of aged folks, and also your young subject's face in order to have a decent chance of aging the subject appropriately.