The NoiseNoise Board
The NoiseNoise board is a hybrid (that's the polite word) hack of two Atari Punk Consoles invented by Forrest Mims III.
(Only he didn't call it that). These are very simple circuits that nonetheless generate interesting and harmonically rich waveforms using cheap and available 556 oscillator chips.
More info on the APC: http://www.jameco.com/Jameco/PressRoom/punk.html, http://en.wikipedia.org/wiki/Atari_Punk_Console