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.
Process Tamer - Freeware Microsoft Windows utility that monitors the CPU use of applications, alerts when they use too much, and reduces their priority to keep your PC fast.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Big Meter Pro - Big Meter Pro is a utility that monitors the disk and memory of your CPU.
Better Uptime - We call you when your website goes down
SysGauge - SysGuage is a responsive software utility that monitors the memory status, CPU usage, as well as network and disk activities of your system.