Here's an awesome tip from WikiPedia's page about Aluminium foil:

A simple and inexpensive way to remove rust from and polish steel surfaces by hand is to rub it with aluminium foil dipped in water. The aluminium foil is softer than steel, and will not scratch the surface. As heat is generated by rubbing friction, the aluminium will oxidize to produce aluminium oxide. Aluminium has a higher reduction potential than iron, and will therefore leach oxygen atoms away from any rust on the steel surface. Aluminium oxide is harder than steel, and the microscopic grains of aluminium oxide produced creates a fine metal polishing compound that smooths the steel surface to a bright shine.