Montastic

I’ve been using Montastic for several years now. I like how it’s simple to use, and does exactly what it says: monitors your sites for downtime. Its free version checks your website every 30 minutes, which is fine for most of my needs. Checking is made from many (US) locations, and the IP numbers of their checkers change “on a regular basis”. A good and solid choice.

Mon.itor.us

I only recently discovered Mon.itor.us, but have already embraced its powerful (and free!) service wholeheartedly. Its interface isn’t too pretty, but when I said “powerful” I meant it- Mon.itor.us will track your site’s uptime (including averages), response times, and visitors. You can build widgets to place on your website, as well.

LinkPatch

There are lots of similar services out there, but LinkPatch is hands down my link checking service of choice. It constantly monitors your site(s) for 404 page views, including links from external sites and out-of-date links you forgot to redirect. It also takes into consideration things like common user misspellings, then automatically emails you details on who got the error, where they came from, and what they were looking for in the first place. Plans start at $10/month, but there’s a free plan if you only need the service for one site.

How do you monitor your sites?