Zentangles - a fancy word for doodles.
And I'm hooked.
P.S. These are my drawings. My sister called one evening and told me to go to YouTube and we were on the phone looking up videos together for a long time. Since then, we both have been drawing Zentangles! She even taught her classroom of kids to do them.
You just start doodling and add on and on to your sketch. Or you draw a shape and doodle inside that shape. Using fine, fine tipped pens is the best for me.
Check out YouTube for other ideas... you might get hooked!
(This link shows how to do some patterns using a large Sharpie.)