BEFORE:Perhaps one of the most useful uses for photoshop has got to be repairing all those old photos that are slowly rotting up there in your attic. You now have the chance, not just to maintain alive a piece of history (which by itself is important enough), but also to learn more about your old, old folks, and let me tell you, you'll be amazed at how much you'll learn from one repaired old photograph.
View: The Guide
This is a very step by step oriented guide that takes you through the process of repairing an old photo. The one used in the example has coloring issues, a rip, tear, and he even goes so far as removing the old white borders that many old pictures had, and he teaches you how to use the cloning tools, blur tools, and so on.
I even picked up a great tip from the guide on how to take scans and rotate them in perfect horizontal/vertical axis alignment.