parts soup, using the battery charger technique to remove rust from many parts at once. I owe Ray Freeman of Perth, Australia the credit for this idea.

You wire the part or parts you want to remove the rust from together and hook the negative battery charger lead to that wire, the positive lead to a piece of scrap metal or scrap tin and shake a fair amount of baking soda in among the parts, then cover it all with water and then plug the charger in, the parts will begin to bubble immediately as the rust is electrochemically broken down and deposits itself on your sacrificial scrap metal, or anode.

for more info on this: http://www3.telus.net/public/aschoepp/electrolyticrust.html