GIMP - GIMP is a multiplatform photo manipulation tool.
FotoFlexer - FotoFlexer is the most powerful online photo editor in existence.
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
Photoshop.com - Photoshop.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
Fun Photo Box - FunPhotoBox is a free photo editing device where you can make clever pictures from your photographs.