Why watercolor? Because we found Barbara Stecher's Sketchbooking earlier this year. It's a nice introduction to travel sketching and note-taking for people who don't draw.
I find sketching a great way to focus when I'm in meetings, lectures, or simply waiting, and this book (published by the DeCordova Museum and so not very well known) is a nice, intelligent way to relax and get the sketchbook off the shelf.
Stecher likes to start in pencil, switch to pen, and then add a little bit of watercolor later. When you get home, drop the sketchbook on your scanner, push a button, and you've got a jpg ready for Tinderbox, email, iPhoto, or for your next presentation.