I thought I'd add some color to this one. I wanted to keep it subtle so I used watercolor pencils which gives me control but still has that transparent wash look. I'm using Staedtler Karat Aquarell Watercolour Pencils which has a pretty nice selection of colors.
I don't think I can call what I'm doing a zentangle. Zentangles are suppose to be spontaneous and shouldn't take more that 15 minutes to draw. With this one, I spent hours messing around with the negative and positive spaces and trying out different designs before drawing it with a pen. I still find it relaxing and I'm definitely in the Zen zone. I'm using a Moleskine 3.5 x 5.5 pocket sketchbook which I love because the paper is indestructible.