Cooking produces all sorts of wastes, from apple peels through turkey carcasses, and boiling is no exception: When you boil potatoes, for example, you'll end up with a pot of starchy water, which will be all the starchier if you peeled them first. Don't throw it out!
It's an effective silver polish: If you have tarnished silver, put it in a glass bowl and pour the starchy water over it after you've removed the potatoes (if the water's still hot, so much the better). And then let it sit, for several hours, or even overnight.
The next morning rinse your silver and dry it with a soft cloth, rubbing it gently to bring out the shine.