CSS for setting up a grid based on 960px.
Play with CSS animations.
CSS framework
CSS for all sorts of things including menus, tabs, loaders, dialogs, etc.
Web safe CSS font stacks and web fonts. Select, preview, and generate CSS and HTML for your font family.
Enter some data and it generates the CSS for the layout of the page
CSS for testing differnt devices and screen resolutions.
Links to many sites with CSS for making menus.
Lots of resources including online generators for creating CSS.
Upload many images in a zip file and it creates one image
Experiment with gradients, shadows, transform, and stroke.
From HTML Goodies
This site shows how the same HTML code can be changed by applying different styles. It's an experimental place for designers to display their creativity.
Everything you need to know about CSS3. There's information and examples to test your browser to see if it supports CSS3.
CSS Tips, Tricks, and Tutorials
Online CSS playground.
CSS3 generator
Provides solutions and workarounds for common flexbox problems.
Shows how to use lists and CSS for navigation
Sass library for creating CSS transitions and animations
A set of small, responsive CSS modules that you can use in every web project.
Demos of common layouts implemented by flexbox.
Enter selectors and it calculates the numbers.
Build buttons, forms, icons, or ribbons.
Doesn't work in Internet Explore