miniPaint - Online graphics editing tool use HTML5 technologies like Canvas, Offline support, Drag and Drop.
JMicroVision - Image analysis toolbox: measuring and quantifying components of high-definition images
JugiPaint - JugiPaint is a painting software with diverse tools for various types of illustration work.
ImageJ - and Other Health Care
RealWorld Paint - RealWorld Paint is an free portable image/photo/animation editor.
Fiji - Fiji: A batteries-included distribution of ImageJ.