When you come from the Eclipse world you surely miss Mylyn (a task focused interface). As I have to use Netbeans at the moment I am looking for something similiar. I would even be satisfied with some little helper to associate some files to a task, so that I can switch my working files at once to work on another project. I know of Cubeon, but it doesn't seem to work with files that are not Java (like Ruby files in my case). It also doesn't seem to be worked on anymore. Is there another little plugin that will do the job?
Task focused features like Mylyn are not available for NetBeans IDE as of version 6.9.1. They may become available after some time due to some community contributions. Cubeon used to work for NetBeans IDE 6.5.1 but I have not tested it on NetBeans IDE 6.9.1 yet, it may work.
Cubeon have initial task focused way of working but need many more features to be compared with Mylyn. So the answer for you is there is no plugin available for NetBeans IDE yet to match Mylyn like features in Eclipse.
UPDATE (11 Oct 2011): There is a NetBeans module for Task Focused Interface in NetBeans IDE hosted at java.net named NBTaskFocus. This module will work for NetBeans IDE version 7.0.x and onwards.