Practical Science

In a similar vein to the experiments carried out by the excellent cmb (see here for hobowine and Hero's fountains) I feel quite a temptation to get back to some actual backyard science. I'll have to be a lot more careful then when I we're a lad though, it appears that most of the bangers and grenades I used to make as a kid could get me 20 years for terrorism offences these days. So does anyone have any suggestions for fun, simple and relatively inexpensive experiments that won't end up with me becoming some guy called Dazzas bitch?

On a similar theme I came across this brilliant site, testing how fast you can spin a standard CD before it simply disintegrates. Trust me it is funny, and somewhat educational.