Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Aggie.io - Draw a picture together with your friends in real-time over the internet in your browser.
Procreate - Procreate is the most powerful and intuitive digital illustration App available for iPad®.
FlockMod - Flockmod is a free real time online group drawing app with all the bells and whistles.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.