I want to take a minute to give a quick shout out to UptimeRobot.

UptimeRobot is a completely free site that allows you to monitor up to 50 websites for downtime related issues.  It polls your sites every 5 minutes, and alerts you via email if anything seems wrong. It’s extremely useful, and did I mention that it’s FREE!? 

The interface is simple to use. Simply enter the URL you want to monitor, and you’re off! You can check back anytime to get statistics on your site’s uptime, and to see when the last “downtime event” occurred. You can also subscribe to your monitors via RSS if that’s something you’re interested in doing. UptimeRobot also includes monitors for pings, keyword checking, and ports, although I am only familiar with the HTTP uptime monitor.

This tool has proven itself useful a couple times already, sending me emails when sites are down, and then sending me emails again when they are subsequently back up.

Overall, a great site, that’s free, and is extremely useful for monitoring client’s websites for down time, or gathering uptime statistics.