Creative Market - Buy and sell handcrafted, mousemade design content like vector patterns, icons, photoshop brushes, fonts and more at Creative Market.
The Y Combinator Database - The definitive database of YC companies with all the metrics
SocialSizes - Sketch templates for sharing images & videos on social media
Startup School - How to start a startup, by Y Combinator
Designify - Turn any photo into awesome, automatically
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.