Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
Animista - Create beautiful CSS animations in your browser
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Keyframes.app - A timeline editor for CSS animations
Platforma - Wireframe library of layouts and UI elements
CSS Animation Cheat Sheet - Awesome CSS3 plugin for spiffy animations