Startup Stash - A curated directory of 400 resources & tools for startups
The Y Combinator Database - The definitive database of YC companies with all the metrics
Freebie.Supply - Awesome free things for entrepreneurs & startups
Y Combinator Companies - Interactive list of all 1000+ YC companies
Stacks - A bookshelf for your online courses
Startup School - How to start a startup, by Y Combinator