I've been meaning to post a link to this site for awhile, but am now finally getting around to it...
Comic Book Innovation is an interesting yet sparsely updated theory-based blog with a couple different comic projects on it. I originally found his site because of his adaption of McCloud's Big Triangle. He seems to also be working on some other projects as well.
While his work isn't necessarily theoretical in a way that explores the medium, it certainly takes a theoretical tact that I haven't seen much in other places. For instance, his Comics Mindmap attempts to break down the constituent parts of a comic, from the parts of a page or panel, up through genre and format. His visualizations of story structure also seem to have some interesting theory based intuitions in them.
One of his projects seems to strive towards creating a "Comic Studio" software program to help comic creators develop works. I'm particularly curious to see what he comes up with, since I've had designs for a visual language software program for over four years now (Alas, I can't code :( ... any enterprising and talented coders out there are welcome to contact me though!).
On the whole, the site seems worth following just to see what curiosities are next to emerge.