Glimpse Image Editor - Glimpse is an open source image editor based on the GNU Image Manipulation Program.
miniPaint - Online graphics editing tool use HTML5 technologies like Canvas, Offline support, Drag and Drop.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
RealWorld Paint - RealWorld Paint is an free portable image/photo/animation editor.
PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
JugiPaint - JugiPaint is a painting software with diverse tools for various types of illustration work.