Bicycle Power Calculator
This is pretty cool (and I originally found it at treehugger). I'm not sure I've entirely figured it out, but if you're at all interested in bicycling as transportation you may find this interesting...it tells you how much energy you have to generate to propel yourself on a bike. Click here to go directly wit the page with the calculator.
It has been recently restored to the web here:
A derived verion is available here:
Amoeba, thanks for the links.