One of the pie in the sky dreams I've always had is the creation of a compact solar panel system that generates enough power to offset the energy needs of a major appliance like a refrigerator or air conditioner for apartment dwellers like myself.
Unfortunately, most residential systems are cost prohibitive, or simply prohibited, for renters like myself (sadly, from my observation, most rental owners aren't interested in such an investment), even with government rebates.
But for folks fortunate to own property with at least half an acre of unobstructed land, with local zoning that allows a structure at least 42' tall and live in an area with a steady breeze of 10mph, you've got the additional option of installing one of these Skystream 3.7 wind turbines. This isn't a small purchase either, coming in around $5400-6100, but the Skystream can offset your power consumption by 20%-90%, while also reducing up to 6000lbs of pollutants that would have entered the atmosphere otherwise.
Perhaps us folks with more humble funds might borrow from this Hong Kong gym, whose interior lighting and television is pedal powered by their exercising clients. Amusingly enough, the gym is named "The California Fitness Gym".