image credit: Gregory F. Maxwell; image source; larger image
Ferrofluids are made of tiny magnetic particles suspended in a liquid. In this image, the ferrofluid pushes above a surface layer of oil and forms spikes along the magnetic field lines of a magnet underneath.
For more images of ferrofluids, check out this picture and the archived Physics to Go feature, "Ferrofluid Fun."
2000 years of magnetism in 40 minutes
Check out 2000 years of magnetism in 40 minutes for an overview of magnetism with an eye toward the history. The lecture is a quick read and includes pictures of magnetism demonstrations.