If you have an apps account (with e-mail), you can "subscribe" to page or whole site changes.  This means that you will be notified by e-mail if someone makes a posting to an announcement or blog page (or any change on any other page on the site that you subscribe to).  Someone makes a posting and all subscribers are notified (without having to send out an additional email).   Further, all the old postings are collected together by date (most recent first) for easy reference.  Postings are esp. useful for meeting minutes, announcements and blogs. 

1. Log on with your username and password.
   
2. Navigate to the page to which you want to subscribe (note: some pages may contain a posting or announcement summary box gadget -- go directly to the actual posting page, not the page that contains the summary box). 
   
   
   
3. Click the "more actions" box in the upper right corner: 
   
   
   
4. Select "subscribe to page changes":
   
5. That's it!  Now you will be notified by e-mail when someone makes a new post or modifies a post.  You can "unsubscribe" the same way.