IsZDown - Monitor the errors and status of the most popular websites and apps. Check whether they are down right now or not.
Site Down - Site down outage and downtime reports from SiteDown.co
DownDetector - A simple service to tell you whether a website is down.
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.
IsItDown RightNow - "Is It Down Right Now" monitors the status of your favorite web sites and checks whether they are down or not.
UPDOWNtoday - UPDOWNTODAY allows you to check whether the website is down or not.