A while ago, there was a picture of a frog, floating by magnetism, making its way around the internet. I re-stumbled on it, along with a youtube video of it (it tries to swim its way out).
For no other reason that its sheer awesomeness, we have the youtube video itself, a non-technical explanation of how this works, and then the scientific paper in PDF format.
Less technical explanation
Technical paper (PDF)