ruby script/plugin install http://opensource.airbladesoftware.com/trunk/plugins/css_dryer/

Create a controller to serve your DRY stylesheets:

    script/generate controller stylesheets

You don't have to call it stylesheets but doing so lets you use Rails' stylesheet_link_tag helper.

Edit the controller so it looks like this:

    class StylesheetsController < ApplicationController
      before_filter :set_headers
      after_filter  { |c| c.cache_page }
      session :off
      layout nil

      private
      def set_headers
        headers['Content-Type'] = 'text/css; charset=utf-8'
      end
    end

Add this line to your routes in config/routes.rb (note the full stop immediately after the word action):

    map.connect 'stylesheets/:action.:format', :controller => 'stylesheets'

You can then put your stylesheets, DRY or otherwise, in app/views/stylesheets/. Once rendered they will be cached in public/stylesheets/.

DRY stylesheet files should have a ncss extension -- think 'n' for nested. For example, site.ncss.

Get them in your views with a css extension with Rails' stylesheet_link_tag helper:

    <%= stylesheet_link_tag 'site' %>

There is currently no advanced documentation for this plugin.