NetBeans 6.0 is now my preferred IDE, it is a great IDE for Ruby and RoR development. It’s very light, having only 19MB (but you also need JDK).
You can quickly get started, NetBeans comes with JRuby, gems and Rails so you can quickly jump to coding and do not bother with installing Ruby, RoR and dependencies. On the NetBeans website there is a lot of documentation about Ruby support including videos. You can also contribute documentation and plugins.
