Hi Nick,
This is quite a long lasting thread. Like the rest, I've recently bought a 2-motor Dagu 5 rover and I also have the motor shield you seem to be using.
Firstly, I have a bit of a problem. Just to test out the Rover, I hooked up the rover to my Arduino Uno just like you have, also neglecting the encoders and I ran your code. When the rover drives, it favours the right rear motor (making it veer to the right). Any ideas on how to remedy this?
Secondly, my rover needs to navigate an obstacle course and hence needs to know approximately where it is. You mentioned above about using the encoders to determine the no. of revolutions of each wheel. Now, I'm what you would call a 'complete novice' when it comes to Arduino and the like and I was wondering how you would go about using the encoders for this purpose. If you had any instructions for me, or could point me in the direction for some help, I would be greatly appreciative. Cheers!