Indian Woodblock Stamps - Use for fabric printing. These are great when you can find them. Use them for stamping in any art project. Can also be found in metal, which are perfect for dipping in melted wax for batik painting.
I never thought about it being a "zen" thing but I've done this sort of doodling since I was in middle school and come to think of it, I'd do it when I was nervous, upset, or overwhelmed. ( I usually 'doodle' when I'm bored)