Extracting and diffing roms

[Camicia]

I am interested to know what tools are available to do a "diff" between ROMs and, if possible, even against the a nandorid backup or some other method to get the file on the phone.

I expect that it would be possible to to extract the content of the ROM on two different folder and then running a opendiff or some other tools on the two folder.

I am trying to see what executable and what script changed between a stock ROM and what I have currently running on my phone or other ROMs available here.

Thank you in advance!