Alcamy - Free, open self-learning platform. Learn & teach anything.
The Y Combinator Database - The definitive database of YC companies with all the metrics
Stacks - A bookshelf for your online courses
Startup School - How to start a startup, by Y Combinator
Airschool - Airschool is a live-streaming educational platform with engagement and monetization tools to help anyone start teaching online. It can be finance, business, wellness, meditation, branding, marketing; in short, anything you want!
Y Combinator Companies - Interactive list of all 1000+ YC companies