The community that is building around Grails is quite amazing to see. Not only has the wiki been translated into three languages (Chinese, Korean and Japanese), but we users contributing code all over the place.
The plug-in system is going to be included in the 0.4 release, but is actually fully working in SVN at the moment, and we have users taking advantage of it already with an OpenLaszlo plugin that lets you generated a Laszlo CRUD application from a Grails domain class.
For those of you who don't know OpenLaszlo is a Rich Internet Application (RIA) framework that allows you to generate Flash or Ajax applications using a more domain specific mark-up. Checkout the examples.