Every summer, or so it seems, the power goes out. And every summer we wish we had enough at-home generating capacity to keep a radio working, to keep our cell phones charged, and perhaps even to keep some computing equipment going.
I collected some reviews of human powered energy devices under the tag crankpower. Here are some excerpts from what I found. Note that I don't have a good answer just yet from personal experience.
Low power, handheld, suitable for recharging a cell phone: the sort of device you're looking at would be similar to a Datex SuperBattery. It's hand cranked, offers a flashlight plus a series of power tips for a variety of phones. You'll see these in flashlight only configurations in any hardware store but the power takeoff is less typical in retail.
Hand crank with a radio: you're looking for something with the feature set of an Eton radio, which does hand crank powered battery driving a radio, lantern, and again some kind of cell phone charger. These have been given out as premiums to public radio station supporters. Again these tend to be relatively low power output.
Foot pedal operated, portable: the device of most interest is the Freeplay Weza, a treadle operated (also 120V and solar panel ready) generator and battery capable of jump starting a car. You pay for the extra battery capacity, but with the variety of input devices this could be the core of a small off-the-grid power system. An exceptionally good review here
I plan on keeping this little puppy. It will do exactly what I wanted. It is a source of emergency power that will keep small electronics up and running indefinitely. I also purchased a 12 volt battery charger for AAA - D sized rechargeable batteries. I was affected by the multi-state power grid failure about three years ago. I realized that if something like that lasted more than about 5 - 7 days, there will be no gas for generators. Solar is a very good option, but it is not easily portable, and is of course sun dependent and needs a storage battery. For real emergencies , this unit would be easy to transport, and should be ready whenever needed.
Bicycle style, stationary: a variety of homebrew devices beckon, calling the skills of the amateur cyclist who is also an electrical engineer. Typical is this discussion on Otherpower of a project that reuses an old 3-speed bicycle, a furnace blower motor and hard drive magnets to generate 100 watts of power. The author notes
I'll have to admit...it's kind of wobbly and a little bit scary when pedaled at full speed.
Bicycle style, mobile: a good extended discussion at Metafilter about adapting a SON dynamo hub to power on-bicycle electronics. The best detailed information is in German only on Rad Forum Lader with a series of plans for making the conversion. It's an electrical engineering challenge, since the SON puts out
nominal 6 volt, variable frequency, variable voltage power, which greatly restricts your choice of parts for voltage transformation and DC conversion.