What do you get when you mix hydrogen peroxide, iodine and dishsoap? Elephant's Toothpaste (or Elefantenzahnpasta, if you prefer German). Many more class experiments from the 2nd link here. [more inside]
Triacetone Triperoxide (TATP), also known as acetone peroxide, is the explosive of choice for Palestinian suicide bombers since it's easily made using commonly available materials. It was also part of the mixture in Richard Reid's shoe bomb. It contains no nitrogen and is thus undetectable by commonly used methods such as NQR, though an effort to cheaply detect it shows promise. What I find most interesting is the way it detonates; unlike most high explosives, it doesn't combust, but instead decomposes rapidly to form acetone and ozone.