If you usually throw away the bones inside fish after eating, stop and think about reusing them. Fish bones make a delicious savoury salt that adds umami flavouring to your dishs.
Just scrape off as much meat as possible, boil the bones until the rest of the meat between the bones falls off. Let the bones dry for a day or two, then grind it up finely in a spice or coffee grinder. The result should be extremely powdery, and you can mix it with an equal amount of salt.
The video above even shows you how to clean the grinder when you're finished -- a method we can vouch for as well.
I usually hang on to fish bones in order to make stock, but this tip from the folks at CHOW is another application of what many people throw into the garbage bin without a second thought.