Spine - Spine is 2D animation software designed specifically for software and game development.
Spirit - The animation tool for the web.
Synfig Studio - Just another WordPress site
Lottie by Airbnb - Easily add high-quality animation to any native app
Unity 2D - Unity 2D is a powerful and feature-rich game design solution built from the ground up to fulfill every basic and advanced need of the developer.
App Animations - Gallery of beautiful iOS animations to inspire your next app