Draft Supply Notebooks
If you are like me and you find yourself constantly scribbling on napkins trying to think through ideas, then you can do no better than to keep them in a notebook. If you don't already have some notebook brand your tied to, then try these Scratch notebooks by Draft Supply Co..
That's what I just did. (In dot-grid if you must know.)
Updated (2016-12-28): The link is dead, so I've reverted to a version stored on the Internet Archive.