Site Down - Site down outage and downtime reports from SiteDown.co
ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.
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.
UPDOWNtoday - UPDOWNTODAY allows you to check whether the website is down or not.
CULA - A webmonitoring solution for beginners and pros.