I've been using Montastic for about eight days now. One of the things I appreciate about the service is the ability to add multiple emails to be alerted when there is loss of service. I currently have a message going to two of my email addresses and it will also send an IM to my cell phone. Montastic can be a little squirelly--it registers false positives when there isn't an immediate response from the server it is checking on. Still, it provides amazingly good service for something free.

Last night it and SiteUpTime.com detected the TechSoup site as being down. Interestingly, the two services showed different amounts of downtime.