has posted a Nintendo Wii Hardware Architecture Diagram recently.
To quote from his page linked above: Inspired by henke37's idea of making a diagram that shows how the different processors on the Wii relate to each other, I took a stab at it. I got a little carried away I guess.
I can't promise everything here is right - there are just too many things we don't know, and even some of the things we do know, we don't all agree on.
So, here's my first attempt at summing it all up...