Groovy is supported in NetBeans via modules available at Development Update Center. http://coyote.dev.java.net project is no longer supported, but most of its functionality is now in this new plugin.
Plugins for Groovy and Grails are currently under development (started in Nov 2007). Here is an overview of what you can currently do with Groovy and Grails in NetBeans IDE 6.0, as well as instructions for getting started.
How To Get Started
In development build of NetBeans you can go to Tools->Plugins and search for 'groovy'. Then select found item and press Install.
How To Submit Issues
Submit issues under top-level Component 'groovy' in NetBeans Issuezilla.
Where Are The Open Tasks?
See the Development Page.
What You Can Already Do With Our Plugins
Don't forget to set Groovy and Grails homes in Groovy options category
Project wizards for Groovy and Grails
Grails project support (open existing or create new, wizards for some Grails components, run project)
Groovy project support (create, run project, execute script)
Groovy editor (basic coloring, formatting, bracket completion)
GSP editor (coloring, highlighting of GSP tags, expressions and scriptlets)
We welcome contributors, let us know if you're interested in extending the Groovy support in NetBeans.