As you all may know already, Blake has given a talk at Defcon about this subject and will be giving two additional talks this year again one if not both about the very same subject. I did some research and found a book by one of the best known Cable Modem Hackers DerEngel The book is called "Hacking the Cable Modem: What Cable Companies Don't Want You To Know"
I am linking to it here.
>$Grey