Marionette Studio - Marionette Studio is an online animation software for beginners and professionals. Animate 2D characters and environments in minutes with no prior skills.
Figmotion - Animation tooling right in Figma
Jitter - A simple animation tool on the web
Spirit - The animation tool for the web.
Principle - Principle makes it easy to create animated and interactive user interface designs.
CSS Animation Cheat Sheet - Awesome CSS3 plugin for spiffy animations