Synfig Studio - Just another WordPress site
Live2D Cubism - Live2D is the world's first drawing technology to enable 3D rendering of 2D images.
AnimeEffects - AnimeEffects is a 2D keyframe animation tool based on deformation of polygon meshes.
Creature - Creature 2D Skeletal and Mesh Animation Tool
Limber for After Effects - IK system for After Effects using shape layers as limbs for character animation
Blender - Blender is the open source, cross platform suite of tools for 3D creation.