JetBrains RubyMine IDE
RubyMine — is the dedicated Ruby and Rails IDE providing intelligent Ruby code editing assistance and tools for web applications development with Ruby on Rails. Find more at official web-site. IntelliJ IDEA is providing similar functionality with the Ruby Plugin installed.
Try RubyMine
RubyMine 4.5.4 is available (released August 2, 2012)
Read what's new in RubyMine 4.5, download and try it.
RubyMine 5 Beta is available (released January 24, 2013)
Read what's coming in RubyMine 5, download and try it.
IntelliJ IDEA Ruby Plugin
Ruby plugin for IntelliJ IDEA is updated according to RubyMine's Development Roadmap. For more details read the FAQ regarding IntelliJ IDEA Ruby Plugin vs. RubyMine.
Plugin is available in the Plugin Repository
Resources
Ruby Plugin 2.0 Release Notes
Recent changes (Updated Jun 8, 2009)
Getting latest version
Ruby Plugin 2.0 Features
Plugin Status
Third-party add-ons
IntelliJ IDEA Ruby Plugin FAQ