Google Alerts is a service from Google that sends email updates to you based on the latest Google results (web, news, etc.) from your choice of query or topic.
You can use Google Alerts to monitor developing news stories, keep tabs on sports teams, or get alerts on topics that you are teaching in your classroom.
I have a Google Alert set up for "physics", "educational technology" and then I add new one's for specific topics I'm looking for.
You enter your search terms, select type (everything, news, blogs, video, realtime, discussions), select how often you want alerts sent to you, volume of results (best or all), and then the email address you want the alert sent to. You can even get a preview of your results before you subscribe.
This is a great way to keep up on trending topics or specific topics for your classes and students can use it for their research.