miniPaint - Online graphics editing tool use HTML5 technologies like Canvas, Offline support, Drag and Drop.
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.
RealWorld Paint - RealWorld Paint is an free portable image/photo/animation editor.
TwistedBrush Pro Studio - A powerful and unique natural media painting program.
Paint XP for Windows 7 - Standalone old MS Paint program that allows you to get your old XP Paint interface in Windows 7.
Corel Painter - Corel Painter is media painting software.