I have a set that I've done (my third) and I haven't posted them yet.
I think that there needs to be more pimping, but the comm itself is a great idea!
As for concrit, I think that you over-do the prompts. I know you're trying to give us lots to chose from, so we don't feel pidgeon holed into doing things we don't like, but it's almost overwhelming. One or two excercizes would be more... do-able and less intimidating. KWIM?
Don't change if you don't want to, but it also seems like a lot of work for you! And just so you know, if you feel bad about scanning pages from books and such, it prompted me to go out and buy Scott McCloud's book and another that he had recced on perspective, so you made them both a few bucks by putting up some of their stuff! :D