Startup School - How to start a startup, by Y Combinator
Go Fucking Work - Website blocker so you can get back to your fucking work
YC World - Explore Y Combinator companies by country
UnDistracted App - Use social media in a useful way. Control Facebook, YouTube, Twitter, Reddit, Netflix and LinkedIn in a responsible way.
Y Combinator Companies - Interactive list of all 1000+ YC companies
CUBI - See your life in weeks