MyPaint is a fast and easy open-source graphics application for digital painters. It lets you focus on the art instead of the program. You can work on your canvas with minimum distractions, bringing up the interface only when you need it.
MyPaint comes with a large brush collection including charcoal and ink to emulate real media, the highly configurable brush engine allows you to experiment with your own brushes. It is similar to Paint in windows but with lot of brushes. Before beginning using MyPaint it is a good idea to read the quick-start tutorial to see how the program is meant to be used.
It has a lot of useful brushes like charcoal, pencils, watercolors, pens. markers, crayons, chalk, etc.
MyPaint has just released version 0.9 (November 2nd, 2010), you can read the changes by visiting this link.
You can install by opening the terminal and typing:
sudo add-apt-repository ppa:tillux/t-misc
sudo apt-get update
sudo apt-get install mypaint