Arduino autonomous tracked robot build Part 3

So I finally got to this step, my bodged together piece of code that makes my robot move. This is the last one in the series.

I uploaded the code to SourceForge so anyone can take it and do whatever they want with it and maybe in the process someone will learn something. Here it is.

Arduino autonomous tracked robot build Part 1
Arduino autonomous tracked robot build Part 2
Arduino autonomous tracked robot build Part 3
Arduino autonomous tracked robot (visual post)

I will start with the easy bits, the small functions and the bits that hold everything together.