Here's yet another faulty idea. My understanding is that electricity is created by spinning a magnet around a wire. I just read a bunch of online sources, and they seem to say the same thing. If it's online, it must be true. All of the different sources of power that we talk about, such as wind, coal, gas, hydro, and geothermal all don't produce electricity directly. Instead, they are the power used to rotate the magnet in the turbine. The main word to concentrate on here is "rotate".
Next up, we have hybrid and electric cars, which always need to find a source of electricity. Now, cars have these four rotating things on them called wheels. Could one embed small electricity generating turbines in each wheel? Essentially, you'd be using the power of the engine to rotate the wheels and then using that wheel rotation to create some more electricity. I just did a bit of reading on turbines and my guess is you wouldn't get more than a few hundred watts out of this, while an electric motor takes thousands, so this would just be a small contributor to the whole electrical system of the car. Maybe you'd get one or two mpgs out of this, not much more. But hey, it's 2 mpgs.
Now, of course these wheel-encased turbines would weigh something and the engine will have to spend more power to make the car move with these heavy embedded turbines. Therefore, this would only be useful if the spinning wheels produced more electricity than the engine used turning the heavier wheels. Hmmm... Would it work?