Jpixel - JPixel is an editor for making pixel art animations and tilesets.
Lottie by Airbnb - Easily add high-quality animation to any native app
Synfig Studio - Just another WordPress site
Spirit - The animation tool for the web.
DragonBones - DragonBones is an open source project for 2D skeletal animation.
Haiku Animator - Create powerful animations for any app or website