Have you ever heard about ferromagnetic fluid? In case you didn't, I'll mention that this is a liquid made of oil and iron (if put simple), that respond to magnetic field. Scince I've descovered the existance of this thing, I want to see it live and have some experiments with it. Until then it seems inevitable to see what is possible with this liquid. I want to mention two examples, that impressed me more or less. In case you know some more, please share.
The first one is a kind of substitute to Lava lamps. It consists of a micro scheme and a tube, a bit filled with the magnetic fluid, with a magnet based in the top part. It is called Ferrocious. Though it is called a substitute I do not fully see it as such. The liquid inside the tube moves according to the music played and is quite interesting to watch. But at the same time the thing is not that big, to enjoy the dance to the full. I wish it would be bigger. The electronic device is accompanied by a smaller glass tube with ferromagnetic fluid, which can be moved by hand with a magnet. This might be really cool for children. Here are some details upon the project.
The second one is of an artistic nature, providing quite unusual and cute color pictures, made of watercolor and ferrofluid. I find this really interesting and inspiring, hope you share my emotions. Enjoy!