Google Alerts can be a pretty cool tool especially if you are looking to track the popularity of a client, product, topic, yourself, or pretty much anything.

http://www.google.com/alerts?hl=en

You simply enter in a topic, your email address and a few simple settings and you’ll receive email telling you when Google indexes a site that talks about that topic. You can specify how often you want to receive emails (daily, weekly or as it happen) and what type of sites you want Google to alert you about (all, blogs, news, etc.)

I’ve used this for my Tornadostream project to find out when people are blogging about it. It’s a pretty nifty little tool!