Spirit - The animation tool for the web.
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.
Haiku Animator - Create powerful animations for any app or website
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
Marionette Studio - Marionette Studio is an online animation software for beginners and professionals. Animate 2D characters and environments in minutes with no prior skills.
Clip Studio Paint - The artist's software for drawing and painting.