Update Scanner - Update Scanner is a Firefox extension to monitor web pages for updates.
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.
WebRSS - RSS Widget - RSS to HTML - Display RSS for Free with Web RSS
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Visualping - Visualping is the easiest to use website checker, webpage change monitoring, website change detector and website change alert software of the web. Read more about Visualping.
Better Uptime - We call you when your website goes down