Startup School - How to start a startup, by Y Combinator
Planny.co - Planny is lightweight Twitter scheduler. Grow faster with calendar planner, multi account management, advanced drafts and analytics.
YC World - Explore Y Combinator companies by country
Gone - An ephemeral to-do list
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.
Day Night - A desktop app that kills the procrastination in you.