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.
Fileion - Fileion is a software-related website where you can download and get reviews software.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Downzen - Downzen.com provides comprehensive reviews and downloads for software in an easy and reliable way.
Better Uptime - We call you when your website goes down
IceWalkers - IceWalkers.com provides a vast database of Linux Software.