Anyone ever hear of Zentangles? It's sort of like structured doodling. It's so portable, I use a 5.5" x 3.5" Moleskin pad and a Prismacolor fine line marker. I can draw anywhere - waiting for an appointment, during lunch at work, in bed or (and this is my favorite) early Sunday morning with a cup of coffee and some mellow music. It's very addictive.