Startup School - How to start a startup, by Y Combinator
Out of Office Email Generator - Personalized, witty OOO replies for guilt-free vacationing.
YC World - Explore Y Combinator companies by country
Rebump - Automatic follow up emails. Keeps on bumping until you get a reply.
Y Combinator Companies - Interactive list of all 1000+ YC companies
Cop-Out - The ultimate excuse generator