A friend of mine showed a Arduino project called Auduino. I non-technical words it’s a synth, but it is also something that:

uses granular synthesis techniques to generate a distinctive filter-sweep sound that had much more character than boring square waves

It is pretty easy to make, and fun to play with. Even thought some of the notes/tones it makes is just noise. What you need is an Arduino, 5 potensiometers and some wires. Hook it all together and upload the library and your set.

Read more about it over at TinkterIt.