UnderStrap - Combines the Underscores starter theme (by Automattic) and the mobil-first, responsive grid framework Bootstrap (by Twitter) into a perfect open source foundation for your next WordPress theme project.

https://understrap.com/

File.io - Ephemeral file sharing Convenient, anonymous and secure. "It's like snapchat, but for files!"

https://www.file.io/

WHAT THE FLEXBOX?! - A simple, free 20 video course that will help you master CSS Flexbox

http://flexbox.io/

Material Design Lite lets you add a Material Design look and feel to your websites. It doesn’t rely on any JavaScript frameworks..

https://getmdl.io/

Pixate - Make your ideas a reality Change the way you design with the most powerful prototyping platform on the planet.

http://www.pixate.com/

Screenings - From typography to logo design, Screenings aggregates the best design-related videos from around the web.

http://screenings.io/

Infinit - Sending files, re-imagined. No file size limit. No waiting. No hassle. Always works!

https://infinit.io/