Some feaures from Rails 2.3 that I wanted to highlight:

Templates

Rails application templates are a way to put project configuration in a single file. Common setup chores like installing gems, plugins, JavaScript libraries, adding initializers, or writing custom rake tasks can be automated with Rails templates.

Use rails app -m mytemplate or a template can even be applied to an existing project. Browsing templates on GitHub is also a nice way to see which tools and techniques other developers are using.

Nested Model Forms

It is complicated but it saves code.

Use Seed Data

Managing seed data in the conventional rails way makes it easier for new team members to figure out how to get development data to work with.

rake db:seed and rake db:setup are new tasks to manage application data while the application code is being developed.