Shine a laser through a drop of water and you can project the image of its flora and fauna on your wall or ceiling. Really. The cat sure enjoyed it!
After witnessing the image of a mosquito in a laser beam outside, I decided to investigate the phenomenon further. I started by locating scuzzy water. Ponds lacking, I decided to take water out of the bowl of my 6 year old spider plant. I then filled a syringe and hung it above a laser so that a drop of water, almost ready to fall, was in the beam path. Below is the incredibly complex apparatus involving a book, sticky-tac, a random bottle, a 250mW laser, and a syringe.
See the setup described in the quote at Teravolt. Link -via reddit
The original link, which has currently blown its bandwidth.