I read an article recently suggesting that coloring has meditative benefits for adults, not just artistic benefits for children. It makes sense: coloring mandalas, for example, requires both the logic of the left brain and the creativity of the right brain. It turns out that googling "mandala" or "complex mandala" will turn up a boat-load of images that are free to print.
Here are some examples (clicking on any of the images will take you to the printable version of it):
I invite you to print one of these and color it as a meditation. Write down what your mood, sensations, and thoughts are beforehand, and when you're finished coloring, write an update. Does anything change? What do you notice? Are you pleased, indifferent, or displeased with your work and the time you spent on it? Why?