Tailwind CSS - A utility-first CSS framework for rapidly building custom user interfaces.
CSSViewer - A simple CSS property viewer
Animista - Create beautiful CSS animations in your browser
CSS Animation Cheat Sheet - Awesome CSS3 plugin for spiffy animations
Instagram.css - Complete set of Instagram filters in pure CSS
CSSGradient.io - As a free css gradient generator tool, this website lets you create a colorful gradient background for your website, blog, or social media profile.