I've had a lot of questions about what I'm using to document/contain this project. I'm using a simple sketchbook that is about 7"x9" that I picked up at my University Bookstore... I'm not sure of the brand though :-/
Really though, you can use anything. You can grab an stack of blank papers and staple them together and call it a day. Or you can doodle in an old magazine or catalog like Justine is doing for a project, or you can grab an old (or new!) binder, punch holes in some blank paper, put it in and call it a day. If you want something a bit more fun and colorful, I suggest these mini books from Elise Blaha.
Want to go shopping for a new simple sketchbook? Try these: