DownDetector - A simple service to tell you whether a website is down.
Is It Down Right Now? - Network & Admin
IsItDown RightNow - "Is It Down Right Now" monitors the status of your favorite web sites and checks whether they are down or not.
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.
Pingbreak - Pingbreak is an original and free monitoring service.
Silent Down - Silent Down is a website uptime and performance monitoring platform - Get notified instantly if your site is down or having performance issues.