Suprvise is a real-time health monitoring and errors tracking dashboard.
WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Is It Down Right Now? - Network & Admin
Monitority - Simple website monitoring service (sms/email alerts)
UPDOWNtoday - UPDOWNTODAY allows you to check whether the website is down or not.
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.