Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Misfit Model 3D - Misfit Model 3D is a 3D model editor that basically operates with triangle-based models.
ShapeShop - ShapeShop is an advanced and professional 3D design and modeling application that comes with an easy-to-use and user-friendly interface.
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.