Kenji Nakamura has taken the reins of my initial work on the Grails Portlets plugin and done an awesome job of refactoring it into more manageable sub-plugins.
You can now plug-in portal implementations with Pluto and Liferay supported initially.
JSR-286 will be supported when the underlying version of Spring used by Grails is updated to Spring 3.0.
Check it out at the Grails plugin portal.
Great work Kenji!