The main method of communication in the Grails community is a set of mailing lists. For each list, there are subscribe, unsubscribe, and archive links.
Mailing list vs. Forum Alert:
If you don't like mailing lists and prefer to use a forum then head over to the Nabble forums, which give you a forum view onto the mailing list. You can also search the archives at MarkMail
You can choose which mailing lists you want to subscribe to on the Grails project page:
Grails User List
This list is for Grails users to ask questions, share knowledge, and discuss issues related to using Grails to develop their applications.
Grails SCM and JIRA List
This list includes notifications of Github commits and activity on JIRA issues.
All Grails Lists
Grails Developer List
This list is for discussion of the development of Grails itself, not Grails-based applications. If you have usage questions, ask on the User list.
If you have trouble subscribing via email you can go to http://xircles.codehaus.org/manage_email and register an e-mail to subscribe.
If you are using gmail to subscribe and you are using an alternate "send mail as" address, it will not work. Use your actual gmail address to subscribe, and make sure you send messages from your gmail account when you send messages to the list.