For all you DJs, this may be a little off topic. But I know for a fact that loads of people use beaTunes for creating spinning playlists. You know, those stationary bikes, installed in endless rows in the your gym. Bicyclists spinning away, generating lots of unused power...
Well, it does not have to be unused. Some small gyms like The Green Microgym actually let you generate real power. Yep, that's right! Your muscle power does not get wasted. And, if you like the idea, you can build a generator bike yourself. Time's Up has detailed plans for the generators they used during OWS on their website and The Green Microgym sells a kit on their site. But there are plenty more. Most likely you can find someone near you, who can help you set up a generator bike.
Wouldn't that be a great New Year's resolution: Never charge your iPhone through a regular outlet? ;-)