Synfig Studio - Just another WordPress site
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Animation Paper - Animation Paper is a software package for doing 2D animation.
Invision - Prototyping and collaboration for design teams
CelAction 2D - CelAction 2D is the name of a powerful and highly advanced 2D animation program for the perfect creation of 2D animation.
Sketch - Professional digital design for Mac.