If you're into Ruby on Rails and are one of the 10 people in the world who aren't using TextMate, you might want to look at the new stuff in the JetBrains RubyMine 3.1 Early Access build.
From the release:
- Autopopup code completion -- no need to press keyboard hotkey to invoke the code completion. It autopops up instantly as you type and works for Ruby, JavaSctipt, HTML and other files. You may want to tweak it -- check IDE Settings | Editor | Code Completion section.
- GitHub integration -- you can open projects in IDE right from a remote repository, or share your project as a new GitHub repository right from the IDE. Read more in IntelliJ IDEA blog.
- Command line application ('mine') -- you can open files and projects in RubyMine from command line now! Just enable the script by running File | Create Command-line Launcher and you are good to command.