A Complete Guide to Flexbox | CSS-Tricks
A Visual Guide to CSS3 Flexbox Properties ― Scotch.io
Flexy Boxes — CSS flexbox playground and code generation tool
Flexbox Froggy – A game for learning CSS flexbox
The Complete CSS Flex Box Tutorial
這篇的圖表還蠻好懂的
CSS Flexbox Tutorial – Vegibit
Visual CSS Flex (Flexbox) Layout Editor / Online Tool
互動式教學，可是介面設計的不太喜歡
很好用的playground
配色很美的教學網站