To begin with I was using just the basic plain text editor like TextEdit, and sometimes I even used Apple’s Xcode IDE, but I wasn’t that comfortable because I needed a core programming editor that is inclined towards Ruby on Rails development.

I am now a days using  TextMate editor. TextMate is highly extensible and useful through a collection of community supplied “bundles”. There are plenty of add-ons that helps in pro development  you can also add language specific short cuts to reduce your typing.TextMate can also be tied up with utilities like Subversion or Rake, which would you to quickly get tasks done without leaving the editor.

There are some opensource free code editing tools available. Although Macosx Leopard comes pre-installed with both vim and emacs. TextWrangler is a free editor from BareBones.  jEdit is another scalable opensource tool made in Java.

Whatever editor you choose, be certain that it provides easy navigation among a large number of open files. Working with Rails applications generally involves dealing with a lot of small files, and that process needs to be efficient. Sometimes I also use Netbeans when I don’t use TextMate.