DC Motor Control using PWM

I am designing a quad rotor helicopter with 4 brushed DC motors. I have the ESC's for them and an arduino Diecimila. I am trying to make this self stabilizing so I need to make a control loop to check motors speed and position of helicopter. Any Suggestions?

Try these two links.

http://www.aeroquad.info/bin/view
http://code.google.com/p/quaduino-ng/

:smiley: