Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting

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.

UptimeRobot - Free Website Uptime Monitoring

Distill Web Monitor - Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.

Simple Ops - Simplify website performance and uptime monitoring with alerting, ssl check, chrome ux metrics, multi locations

Update Scanner - Update Scanner is a Firefox extension to monitor web pages for updates.