If you've built your fair share of PCs over the years, you probably have quite a few old fans lying around. Here's how to quickly give them a purpose by turning them into small wind generators.
To start you'll need an old PC fan (the bigger the better, obviously), a thick plastic bottle, an old CD, some wire, some Schottky diodes, and a few miscellaneous craft supplies. You'll need to know how to solder, too, but beyond that, it's a pretty simple hack. You won't actually use the fan's blades in your final turbine—they're a bit too small—but a cut-up shampoo bottle works perfectly for some blades that you can then glue onto the fan's motor.
Obviously this isn't going to power your house, but if you're looking for a fun project that will save you a few wall outlets (which are precious commodities in the homes of us techies), this'll do a great job of recharging the rechargeable batteries on your more power hungry devices. The above fan puts out 1.5v and 20ma, for those of you interested in the exact specs. Hit the link to check out the full instructions.
Upcycle Your Old PC Fans into Mini Wind Generators [Instructables via Unplggd]