Lottie by Airbnb - Easily add high-quality animation to any native app
Synfig Studio - Just another WordPress site
Marionette Studio - Marionette Studio is an online animation software for beginners and professionals. Animate 2D characters and environments in minutes with no prior skills.
Spine - Spine is 2D animation software designed specifically for software and game development.
Spirit - The animation tool for the web.
Animation Paper - Animation Paper is a software package for doing 2D animation.