OpenToonz - OpenToonz is an animation program that is a free software version of Toonz, the animation software...
PaintBerri - PaintBerri is a free art site that offers an awesome oekaki community.
Synfig Studio - Just another WordPress site
okekai - A small community site where you can draw, animate, and chat through pictures all for free
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Brush Ninja - Hand-drawn Animated Gif Creator