Site Down - Site down outage and downtime reports from SiteDown.co
Is it Down? - Is it down can check if a website is down or is it just your PC that can not access it.
DownDetector - A simple service to tell you whether a website is down.
UPDOWNtoday - UPDOWNTODAY allows you to check whether the website is down or not.
Outage.Report - See if your provider or web service is having an outage or it's just you. Post yours and see other's reports and complaints
Is it up? - A simple tool to check if a website or ip address is up or down.