Most Web users are familiar with Web and RSS alerts (see our How-To on Google Alerts) that send you notes whenever a term you're interested in is mentioned on the Web. Smart marketing managers set up alerts for their company and products; many people I know also have alerts set on their own names. You can also scan for news terms you're interested in.
And now you can get alerted whenever someone Twitters about you or your company. Just send a Twitter message "Track [word]," and whenever someone uses that word in post, you'll get a copy of it. As with regular Twitters, you can have track alerts sent to your Twitter Web page, an IM window, or SMS.
You can turn off tracking by typing, "Untrack [word]," and get a list of all your tracks by sending "Track" by itself.
It's a good way to find people who are discussing items you care about.
(Minor bug: Actually, Twitter Tracks treats "track" and "untrack" identically, as toggles. In other words, if you want to track "Webware," you can type either "track webware" or "untrack webware." To turn off tracking on a term you're already following, likewise, either command will do the job. This is no big deal if you know about it, and Twitter sends confirmations after each command that tells you what you're turned on. Or off.)