This is a quick and dirty instructable.
Step 1: You Will Need ..
Step 2: Salvage the Voice Coil and Magnets From a Hard Drive
Step 3: Assembly and Operation
Mount the magnets around the coil just as they were in the HD.
Tie a long length of ribbon to the heads on the voice coil.
Solder a couple of pieces of magnet wire to the contacts of the voice coil.
Solder the other ends of the magnet wire to a LED.
To operate, hold the wind belt in front of a fan with one hand and dynamically tighten the belt with the other, to light the led takes a fairly low frequency ( And consequently high amplitude).
Future steps, frame, rectification