OpenToonz - OpenToonz is an animation program that is a free software version of Toonz, the animation software...
Synfig Studio - Just another WordPress site
Toon Boom Harmony - Production-ready animation software for every artist, in any style.
Adobe Animate - Adobe Animate is a Flash, vector animation software.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Animation Paper - Animation Paper is a software package for doing 2D animation.