What's the secret sauce in Ruby on Rails?

Ruby on Rails is a great framework for writing web applications. The web app that I'm writing now is so nice with RoR, I really like the idea of conventions over configuration. In previous projects I've worked on, I've really tried to use one convention as much as possible, whether it be a convention that I came up with, or an existing one. With this, you can do some really powerful things, especially if you use a very powerful editor, such as the editor I use, Emacs.