I read an interesting post recently on the different uses of Google Apps Scripts ranging from Twitter out-of-offices to self-destructing messages. One of the uses I found particularly interesting is the ability to track your web site's uptime and get alerts when there's a problem, all completely free!
There's various tools available for monitoring a web site's uptime, Pingdom and Uptime Robot to name a couple, but few that are free and as quick to implement without any upselling for premium services. The script developed by Digital Inspiration uses embedded code in a Google Docs Sheet to monitor your web site at 5 minute intervals and then log it in the same sheet for analysing.
While this solution may have limited features, to easily get a notification when you're server is having issues this is a nice freebie... The alerts are unlimited, it's easy to implement and can be setup for multiple domains.
I tested this myself by adding two domains, www.codesynthesis.co.uk and www.codesynthesis2.co.uk (which doesn't exist), sure enough after 5 minutes I got an email notification to let me know my non-existent site was down. Not bad for a google docs sheet!