Damien Haw has written a great tutorial on restoring an old torn photograph using Photoshop although I suspect the same techniques can be used in all of the other sophisticated photo editing programs. It is an interesting step-by-step instruction in using many of the available tools.
Professional Photograph Restoration Workflow may be found at http://psd.tutsplus.com/tutorials/photo-effects-tutorials/professional-photograph-restoration-workflow/
