This ‘ere stuff is a magnetic liquid called ferrofluid making some extremely strange waves. The rather excellent Dansdata site has a great article all about magnets, and the cool and wonderful things you can do with them. I like Dan’s site, it’s full of quirky geek stuff – like an evaluation of toothpaste as a thermo paste, or how to destroy your PC – all done in an offbeat Aussie style.
Mentioned in the article is the Force Field site which sells a whole heap of different types of magnets. Cool stuff.