NetBeans is expanding to new developer communities by adding support for various scripting languages. We did Ruby for 6.0 and in 6.1 the Groovy support looks very interesting (see Martin Adamek's blog for details or you can watch the progress on the Groovy tasks page). I plan to demo Groovy support in NetBeans during next week in Cologne so keep your fingers crossed.
The other language whose developer community happens to be very large is PHP. I've been using PHP for many years before Sun so I am quite excited to see it being supported by NetBeans as well (and it will be easier for me to evangelize it - I actually developed a large e-commerce application in PHP). The plug-in is available on the update center of 6.1 or 6.0 (the older version) and it's still rather in it's infancy - sorry no refactoring yet :) However there's one particular feature which I thought was cool - integration of bigmanual into code completion. I switched so many times between the editor (Homesite, Zend, Quanta, ...) to the browser to see the bigmanual... I wish I would have had such a feature back then, it would have been a big timesaver!