If you want to start playing with the latest features of Ruby on Rails (2.0 due out very soon), you can install from source with something like the following:

sudo gem install rails --source http://gems.rubyonrails.org -y

To verify your install,

rails --version

Background

What do I mean by externalizing? I really mean addressing separation of concerns and making an application more portable. If you think about it, a configuration is a module that other modules in the application depend on. By separating the concerns or behaviors of an application that varies between development, test, and production environments, you can more easily manage and possibly reuse the configuration and not repeat yourself (DRY).
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