Cloud Tools has both Maven and Grails plugins. Thanks to Dustin Whitney the Grails plugin has all of the features of the Maven plugin. Below is a short screencast showing how to deploy a Grails application on Amazon EC2.
And one quick reminder: if you want to lean more about running Java and Grails applications on Amazon EC2 then check out my upcoming February 17th half-day and inexpensive class in Oakland, CA.