Startup School - How to start a startup, by Y Combinator
Startup Rocket By Buildily - The best startup tool kit for founders in one membership
The Y Combinator Database - The definitive database of YC companies with all the metrics
Startup Toolkit - Interactive how-to guides to launch your startup
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.
JumpStart Toolkit - A pack of tools and goodies to jumpstart your startup