ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.

Is It Down Right Now? - Network & Admin

AppZero - AppZero is a monitoring and migration tool that allows users to keep track of different applications and servers in both simple and complex IT environments.

Site Down - Site down outage and downtime reports from SiteDown.co

Netumo - Ensure healthy website performance, uptime, and free from vulnerabilities. Automatic checks for SSL Certificates, domains and monitor issues with your websites all from one console and get instant notifications on any issues.

IsThisSiteDown.org - Free tool to check whether a site is down just for you, or for everyone.