Hydrogen peroxide is also useful for anyone who likes to make big, loud, colourful explosions.
Mix 30 ml of 20 volume hydrogen peroxide solution with 20 ml of ethanol. Light the mixture, add 0.5 g of potassium permanganate and stand back. You are guaranteed fun.
These figures are given by http://www.cce.paisley.ac.uk, which also suggests you carry out the reaction in a fume cupboard and light the mixture with a taper. However having seen it carried out by a teacher this morning, I can confirm it is perfectly safe to do it in open air and get the flame going with a cigarette lighter.
What actually happens is this. Hydrogen peroxide is unstable and decomposes (even at room temperature, though slowly) to oxygen and water. Potassium permanganate is a very good catalyst for this decomposition, so the hydrogen peroxide will decompose much more quickly. In the above demonstration, this decomposition takes place underneath burning ethanol. The oxygen being released, which of course at this point is pure rather than at 20% as in air, is thus exposed to the ethanol. Oxygen is naturally a good way to encourage fire (considering that combustion is oxidation), so the low-level flames on the ethanol erupt into a column of explosions.