Baking soda is great for removing rust, and as an added bonus, you probably already have plenty in your house.
Mix baking soda with just enough water to make a paste that can nap your tools without it all dripping off. Apply it to the rusted area and let it sit for a couple of hours so it can get to work. Then the tool should be ready to scrub, scrub the rust off with a clean toothbrush or a rag. Rinse all the excess off with some water and dry thoroughly with a towel, otherwise your freshly cleaned tool may rust again.
The acid in lemon juice makes it an all-natural cleaner, and great for removing rust stains.
Start by rubbing salt all over the rusted parts of your tools. Once coated, squeeze a lemon all over the salt-coated area and let sit for two hours. This will loosen the rust and from there you can just scrub it off. For super tough rust stains, try using steel wool or a scouring pad, and a little bit of elbow grease.