I have been a Java programmer for a long time and a big fan of eclipse. Lately I have been very interested to try out Ruby on Rails and Python with Django. I am not the guy who wants to program using text editors. I found that we have these following choices. I have listed here some IDEs and simple test editors which can turn into powerful programming environments for you as a new RoR explorer.
Programming environments listed in Alphabetical order
Note: If you are already using a tool for Ruby on Rails development, please leave a comment and let us know about it.
Eclipse based RadRails - If you are coming from Java shop and are already heavily into eclipse as your IDE, then you might want to check this out. It installs on Linux, Mac OSX and Windows. Because eclipse is java based, you will need jvm installed before you install RadRails with eclipse. RadRails can also be installed with Aptana Studio, an IDE bundle by RadRails creators.
JEdit - JEdit is a powerful programming tool for those who are good with using just a text editor for their coding requirements. Here are couple of good guidlines from Eric and Eadz for working with JEdit for RoR.
NetBeans- This is a java based IDE which has a good support for RoR. Comes bundled with Glassfish V3 Prelude. They provide RoR learning trails that can help you if you are a beginner.
TextMate - For all Mac enthusiasts, this is the editor of choice for RoR. This is pretty powerful and highly customizable. You defenitely want to check this out if you are on a Mac. If you use windows, there is a similar editor called eTextEditor, which is equally powerful.