Pixelitor - Pixelitor is a cross-platform raster graphics editor written in Java.
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.
RealWorld Photos - RealWorld Photos is an free portable photo editor for Windows.
JugiPaint - JugiPaint is a painting software with diverse tools for various types of illustration work.