Go to: http://www.google.com/alerts fill in the search query line with the information your searching for, adjust the other fields to meet your needs (result type, language, region, how often, how many, and deliver to email address). Once these are set, you're set. You can manage your searches over time as well, adding new searches, dropping old ones, editing those you need to hear more from.
This service could be used to keep track of how often and by whom your blog is mentioned, you are mentioned, where specific jobs are being sought, what the most recent stories in a particular field are. Authors with thick enough skins could keep track of their books to see what reviewers and others have to say. Bloggers might find it a way to link up with other bloggers with similar interests. The possibilities go one, limited largely by your own creativity.