GIMP - GIMP is a multiplatform photo manipulation tool.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
ShapeShop - ShapeShop is an advanced and professional 3D design and modeling application that comes with an easy-to-use and user-friendly interface.