The Y Combinator Database - The definitive database of YC companies with all the metrics
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Startup School - How to start a startup, by Y Combinator
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Y Combinator Companies - Interactive list of all 1000+ YC companies
Better Uptime - We call you when your website goes down