I found this great instructable about hacking dynamo keychain flashlight into a nice 5v power supply. They use a MAX756 step-up DC-DC converter and a few other parts to get it all working. This looks like a really interesting idea for remote applications where power isn’t readily available or a solar panel would be too bulky or fragile.
Now you can have a regulated power supply constantly at your fingertips with NO batteries to replace or recharge! This Instructable shows you how to modify a keychain dynamo flashlight into a lean mean supply that can replace batteries for any projects requiring quick 5 volt direct-current (5V DC) power.
More about making a Battery-free 5 volt project power
In the Maker Shed:
MintyBoost USB Charger Kit v1.2 – Build your own MintyBoost: a small & simple (but very powerful and very MAKE-like)USB charger for your iPod (or other mp3 player), camera, cell phone, and any other gadget you can plug into a USB port to charge.