Hook up a small generator to a home's incoming water supply line, or maybe just the line to the water heater. There's enough pressure there to produce 25 watts or so, enough to recharge whatever rechargable gizmos - cell phones, MP3 players, GPS units, etc - we might have.
Here's a geek who loves his cat.
Take an old automobile diesel engine and mount it on a small trailer. Mount dual alternators, a hydraulic pump, and an air compressor on the engine. The dual alternators would provide 24 volts, which would allow it to be used to recharge the battery bank in an off-grid power system. They could also be used to provide power for electric arc welding. The hydraulic pump could be used to drive a wood splitter. Compressed air has any number of uses. This would be just the thing for off-grid DIY home builders.