Gimp
Gimp is a freely distributed software for editing tasks as photo retouching, image composition and image authoring. www.gimp.org
Inkscape
Inkscape is a Vector Graphics Editor, similar to Adobe Illustrator, that strives to be SVG Compliant, open source, responsive and extensible www.inkscape.org
Art of Illusion
Art of illusion is a 3D-modeller, renderer and raytracer. It is written in Java and runs on Linux, Solaris, OS X, and Windows. www.artofillusion.org
Creatoon
CreaToon® is a powerful software solution for the PC to create 2D animation in the cut-out style. www.creatoon.com
Jahshaka
The worlds first Open Source Realtime Media Playback and Visual Effects System www.jahshaka.org
Audacity
A free, open source software for recording and editing sounds in Linux, Mac OS X, and other operating systems. audacity.sourceforge.net
Blender
A powerful open source, cross platform suite of tools for 3D creation www.blender.org