In the August issue of GroovyMag, guest plugin-corner columnist Keith Cochran covers the new Clojure plugin by Jeff Brown. This plugin allows you to include Clojure source code in src/clj and then access that code in your Grails application. More details on the Clojure plugin can be found at http://grails.org/plugin/clojure.
A while back Vaclav Pech came out with a similar Grails plugin for Scala. This one hasn't been covered in GroovyMag... yet. Anyhow, you can find out more about this plugin at http://grails.org/plugin/scala.
So now in a Grails application you can have Groovy code (all over the place), Scala code in src/scala, and Clojure code in src/clj. That's pretty impressive! As I was marveling at these recent developments, I realized that Grails now supports 3 out of the four languages covered in Stu Halloway's paradigm-shifting blog series on Java.next (Groovy, Scala and Clojure - no JRuby... yet).
So unless something else comes along that as easily supports all four, I think we can safely call Grails the "Official Web Framework for Java.next".