If you've got a 16 tesla magnetic field, you can levitate a frog.
The levitation trick works because giant magnetic fields slightly distort the orbits of electrons in the frog's atoms. The resulting electric current generates a magnetic field in the opposite direction to that of the magnet. A field of 16 teslas created an attractive force strong enough to make the frog float until it made its escape.
Best part: it doesn't kill the frog. (via afrooz)
Update: Video of the levitating frog:
See also levitating strawberry, levitating grasshopper, and levitating water droplets. (thx, jesse)