YC Interview Practice App - Get asked YC questions by Sam Altman
BetaList - BetaList provides an overview of upcoming internet startups. Discover and get early access to the future.
Pramp for Product Managers - Practice product management mock interviews with other PMs
Loot - Loot is a bank account ledger.
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.
StartupBase - Community of makers & early adopters