If you track information on a batch of discrete topics all the time like I do, managing your inbox is no day at the beach. Monitoring a number of mailing lists for interesting news on, say, [harry potter] or [sony aibo] or [housing bubble] without actually subscribing to what could be hundreds of mailing lists is a daunting task. (And remember, Google Groups also encompasses Usenet groups - even more messages to scan!) There hasn't been an easy way to achieve this in Google Groups except for periodically searching for a given topic to see if there are any new and interesting posts.
Some of us thought it would be cool to offer a feature that does this work for us. Whenever we start thinking like this, it's usually followed by a new product - and that has led to our latest Alerts offering, a beta version of Google Groups Alerts. It monitors the top 50 most recent Google Groups search results that relate to keywords you're interested in. Any new articles posted that match your criteria will be emailed to you, just like Google News alerts. The ideal candidates for Groups Alerts are those that might be discussed in multiple discussion groups. Give it a try and see if you don't save time - and stay current.
