Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Spine - Spine is 2D animation software designed specifically for software and game development.
MakeHuman - MakeHuman is a free, open source, interactive modeling tool for creating custom 3D human characters.
Synfig Studio - Just another WordPress site
ZBrush - ZBrush is a digital sculpting and painting software solution.
AnimeEffects - AnimeEffects is a 2D keyframe animation tool based on deformation of polygon meshes.