We were playing with some glasses and a loudspeaker - as one does - and we were using a piece of paper to indicate when we were getting close to a resonant frequency. It then jumped off the side of the glass and started to levitate.

The tube at the top has a speaker in it, and we were driving the glass very close to a resonant frequency - I think this was a resonance in the air in the glass not in the glass itself

We also took a couple of movies of this

Short film - 600kB

Longer film - 8MB

You may want to turn down your speakers...it was loud!

I assume it is a similar effect to how the sand moves away from the anti-nodes (regions with the most vibration) in the standing waves on a chladni plate. If you have a region which is vibrating violently and a region that is vibrating less violently, and there are particles jumping around they will be pushed a long way away from the violent region, but because it is calmer in the quiet region not so far away from the quiet region, so they will move towards the quiet regions.

It is loud in the glass as there is a resonance there and quieter outside, so it is moved outwards

Generally just cool though!