GIMP is a freely distributed program for such tasks as photo retouching, image composition and image authoring. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, and more. Available also as portable app: http://portableapps.com/apps/graphics_pictures/gimp_portable
- GIMP is a very well featured image editor for both simple and complex editing. It can be pretty hard to starters to get used to simple tasks but it's worth trying.