Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.

Startup Playbook by Hatch Quarter - A guide to building your startup

Eduflow - Digital learning that actually teaches students something

On Slack by Standuply - The most extensive book on using Slack to the utmost

Kialo - Kialo is the platform for rational debate. Empowering reason through friendly and open discussions.

CS183B - Startup Class - Stanford class taught by Sam Altman & guest speakers