I found a lovely Celtic Tree of Life mandala for you to color at http://www.supercoloring.com/. There are also other celtic symbols and images there to color if you want more. I love this Celtic Tree of Life design and think it is very different from other mandalas for coloring that I have posted. And this one you can even color online if you don’t have coloring tools!
I found a great video by Indiga Healer that shows you step by step how to go about drawing a mandala quickly and beautifully. As the title suggests, drawing a mandala every day can be very therapeutic on many levels.