I'm signed up for the Chicago Marathon and I'm training by myself using the Non-Runner's Marathon Trainer.
This is a book that comes out of a class at the University of Northern Iowa that is a joint class between a psychology professor and a phys. ed. professor -- the phys. ed. professor brings the training you need to complete a marathon and the psychology professor brings a lot of self-helpy stuff about the mental preparation you need to get through the training process and then the race itself. I'd make fun of the self-helpy stuff, except that it seems to be helping already. And the book is aimed squarely at the non-runner and getting you to complete a marathon. Not do it with a great time or lose a lot of weight or any other side goals -- simply complete a marathon. Since that's what I'm trying to do, it seems like the perfect training program for me.
You can follow along with my Marathon progress on my main blog, if you like.