CatLight - Shows build status in your tray
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.
CCTray - Display continuous integration status from most build servers.
UptimeRobot - Free Website Uptime Monitoring
CCMenu - CCMenu displays the build status of projects on a continuous integration server as an item in the...
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring