Mirah-netbeans-plugin is a project mainly written in JAVA and MIRAH, it's free.
A plugin for editing and compiling Mirah code in Netbeans.
To use this you need to replace Netbean's jruby-parser with the duby version. I use this command $ cp duby/javalib/JRubyParser.jar /Applications/NetBeans/NetBeans 6.7.1.app/Contents/Resources/NetBeans/ruby2/modules/ext/jruby-parser-0.1.jar