sound - electricity?
J_McQuade: When it comes to power from sound, be warned that results are likely to be rather disappointing - there's a reason microphones and guitar pickups benefit from such highly sensitive pre-amps! If you're just looking to do it out of intellectual curiosity, though, then piezos will at least get you somewhere - like DC motors, they're a 'two-way' thing; put power in, get vibration (sound), put in vibration, get (a little) power. You can often scrounge them from old toys, too, so they might be worth a look.Other than that, there are a few interesting projects out there looking at alternatives to turbines for generating wind energy - my favourite would have to be this one:http://www.popularmechanics.com/technology/industry/4224763....Cobbling one of those things together could make for an interesting and fairly cheap project - if you find the time to do it then I'd love to see the 'vital statistics' of how much juice it'll give you!