Yes, selling them for parts is a good idea, expecially if cosmetic conditions are good. Some people only needs the leatherette or the shell, or the lens' bayonnet.

If you have a technician who always took good care of your gear, you may consider presenting it to him for spare parts. I usually do this with mine, as in turn I'm very glad when he pulls out a missing piece for one of my cameras, taken from someone elses' broken unit.