Chris and I were making tomato sauce this weekend. We blanched the tomatoes, and put the skins in a different pile. At the end of blanching, Chris suggested, "What if we put the skins in the food mill?" I thought it couldn't hurt anything. Guess what? We milled the skins on the finest screen. The skins will not go through the screen. But we got about a cup of tomato juice out of them. (5-8lbs of tomatoes)
So, the next time you blanch tomatoes to peel and make sauce, mill the skins before you discard them to get all you can out of the tomato.