Ferrofluids are basically just iron nanoparticles suspended in a liquid. In the presence of magnets, they do some pretty cool things. For instance, ferrofluids flow to place where the magnetic flux--the strength of the magnetism--is strongest. So if you magnetize the screw from a meat grinder so the magnetic flux is denser at the top than it is at the bottom, the ferrofluid will climb the screw like staircase.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.