You no longer have any excuses for not using Flexbox for your page and apps layouts.

• A guide to Flexbox by CSS Tricks. Best resource for getting started with Flexbox

The previous link from Chris Coyer should have everything that you need but feel free to browse the following list.

• Nettus CSS Flexbox Examples
• Using Flexbox
• Dive into Flexbox
• Working with Flexbox the new spec
• CSS Flexbox Please!
• Centering elements with Flexbox
• Solved by Flexbox
• The Ultimate Flexbox Cheatsheet
• Vertical centering with Flexbox + margin fallback
• Flexbox: center horizontally and vertically
• Flexbox Grid
• Easy Masonry Layout With Flexbox
• Real World Flexbox
• Webkit Flexbox Patterns
• Designing CSS Layouts With Flexbox Is As Easy As Pie
• Learn CSS Layout