YC Interview Practice App - Get asked YC questions by Sam Altman
The Y Combinator Database - The definitive database of YC companies with all the metrics
Pramp for Product Managers - Practice product management mock interviews with other PMs
Startup School - How to start a startup, by Y Combinator
Swyg Interview Practice - Practice interviewing in live video chats with a partner
Y Combinator Companies - Interactive list of all 1000+ YC companies