The Google Gadgets directory contains a lot of useful Gadgets and news feeds. If the RSS or Atom feed is not in the directory (yet), you can also directly add an item to your personlized page by pointing to a RSS or Atom url.
Off course I created a new personlized page containing all the news feeds related to Grails, so I can see the latest activity very easily ;-)
If you want to add them to your own personlized page just click the links below:
Grails User List
Grails Dev List
Grails JIRA Activity
Grails Build Status