One of the best ways to preserve old photos is to copy the negatives with a digital camera and then use image processing software to "develop" the photo.
I built a setup for digitiziation with a DSLR to process my old negatives some of which have a sentimental value.
Since I do not have a macro lens, I combined an SLR lens with a couple of cheap adaptors. The rest was improvised from pieces of wood, cardboard , PVC and even meccano parts.
NOTE: Check out a recent update of this instructable!