Graphics

Blender is the free open source 3D content creation suite, available for all major operating systems under the GNU General Public License.
http://www.blender.org/

Inkscape
An Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format.
Inkscape supports many advanced SVG features (markers, clones, alpha blending, etc.) and great care is taken in designing a streamlined interface. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more.
http://www.inkscape.org/

YafRay
YafRay is a powerful raytracer, under the LGPL license. It enables you to create fantastic images and animations of a photorealistic quality.
Link