The Google Blog announced that they have added Google Blog Search email alerts to the Google Alerts system. So like you were able to add alerts for Google News and other Google properties, you are now able to add alerts for Blog Search results. Google has also enhanced Alerts to “show results from multiple sources (including Google News, the web, and blogs).”
You can either conduct a search at Google Blog Search and click on the “Blogs Alerts” link on the left hand side of the page to subscribe via email to news alters. Or you can go to Google Alerts to set them up directly there.
I personally use RSS, so I had a form of Google Alerts set up via RSS a while back. But the “Comprehensive Alert” is very cool and I kind of wish they had a single RSS feed for just that.