Recently, I've been doing all my writing and drawing in little soft cover Moleskine sketchbooks. The books are a little smaller than 4x6, and for me this is the perfect size. It's easy to have it and a pen in my pocket, and I can pretty much draw anywhere and anytime as a result. If I have a little time before my day job, I can sit in a coffee shop and get a few panels in. If I've arranged to meet someone, and they're running a little late I can do a little bit of work while I wait. It's very convenient for fitting drawing into the little spaces when life gets hectic.