These are all links I frequent, work with, or highly recommend. I will be adding to it over time so be sure to bookmark this page for great CSS Resources.
Learn CSS
How to Customize Your WordPress Website’s CSS – Elegant Themes
A comprehensive list of CSS & CSS3 definitions and lessons – w3schools.com
Introduction to CSS selectors – creativebloq.com
CSS Tutorials (Beginner, Intermediate and Advanced) – htmldog.com
Free Pro CSS Hacker Course – stacksocial.com
Font Tricks
Inspiration for Text Styles and Hover Effects – tympanus.net
Adding Stroke to Web Text – css-tricks.com
Text Shadows, Outlines Neon Glows and more – w3.org
How to add custom fonts in WordPress – wpsites.net
Block Quotes
How To Customize Blockquotes Style in WordPress Themes – wpbeginner.com
Really Cool Modern Block Quote Styles – tympanus.net
Box Shadows
CSS Box Shadow – css-tricks.com
Image Filters
Add Color Filters to Your Images – codepen
Separator Styles
Some inspiration for flat divider styles – tympanus.net
A Collection of Separator Styles with instructions – tympanus.net
Transitions & Animations
An Introduction to CSS Transitions & Animations – elegantthemes.com
CSS3 Animations – w3schools.com
CSS Shapes 101 – alistapart.com
CSS Animation for Beginners – robots.thoughtbot.com
Simple CSS3 Transitions, Transforms, & Animations Compilation – callmenick.com
A Collection of Cool Hover Effects for Links, Buttons, Logos, Featured Images and More – ianlunn.github.io
Swinging keyframe animation – dynamicdrive.com
A Collection of CSS3 Powered Hover Effects – ianlunn.github.io
8 Simple CSS3 Transitions That Will Wow Your Users – webdesignerdepot.com
Underlines
CSS Sliding Underline – bradsknutson.com/