Hello.

I have discovered for myself (I don't know if anyone else has) a way to power a Power Functions M-motor with out batteries

It's very simple.
1)Place a crank on one m-motor
2)Plug m-motor into another m-motor
3)Turn crank

The opposite motor thens spins either clockwise or counter-clockwise, directly affected by the direction you turn the crank.

I have no XL-motors, and no more than two m-motor, so I haven't experimented with XLs or more then two m-motors.

Also, I am not sure if and how badly this abuses the motors.

Copy and paste this URL into your address bar for a video I took:
http://www.youtube.com/watch?v=dQgC5qQgAYw