Build an Easter Egg Anemometer
by Lloyd Alter, Toronto on 03.24.08
No doubt all the green living sites will have tips today about how to recycle your plastic easter eggs, instead of asking why you bought them in the first place. Only Instructables would suggest you use them to build an anemometer, which "goes together quickly if you have the parts laying around. This is basically a mini wind generator; the spinning motor produces a current that a multimeter reads." ::Instructables via ::Lifehacker
too complex; built one years and years ago and there are better directions online too.
USE bike speedometers! great use for an old bike meter. if you don't have the 'sensor' buy a reed switch. If you can't adjust the wheel diameter that small (which I couldn't) then you have to do a little math-- but the bike meter will give you speed, max speed, odometer, etc. you just have to do a simple multiplication to get the real number! (unless your meter lets you set a small wheel size; you could build the eggs out so they are the same radius as the smallest wheel size supported by your meter.)
Not to mention bike meters use tiny 1.5V watch batteries that last for years and you could replace with something larger or solar panel... (well, I always had planned on a large cap with a solar panel but never did it)