YC Interview Practice App - Get asked YC questions by Sam Altman
Startup School - How to start a startup, by Y Combinator
YC Interviewer - Are you ready for an interview with investors?
SkySilk - SkySilk Managed Cloud Services, Offers Free Cloud Resources
YC Random - Random YCombinator interview questions every 10 seconds
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.