I was a bit bored so I whipped up this little diagram in OmniGraffle of the control flow within the PINQ framework and an application. Most things will seem familiar to programmers who regularly use MVC frameworks. It's actually slightly more complex than what is going on in there; however, I was limited to using 20 object with the demo version of OmniGraffle and so I was rather limited on what I could show.
The one interesting bit in here is the yield resource exception. As I've written in previous posts, it changes control from one controller to another.