I keep a second sketchbook at work in case I want to draw something. It doesn't fill up nearly as quickly as my sketchbook at home, but that's because I'm usually, you know, working.
Since its usually quick doodles, it never really take long to jot something down during lunch, while I'm rebooting my machine, waiting for a long deploy, or syncing through our SVN. I figured it was important to scratch the itch when it comes to me, to encourage the urge to draw rather than putting it off. And with the cre8ery literally around the corner from the office, having pencils and such isn't an issue.