Controllerを作らずにViewを表示したい ref: http://qiita.com/jacoyutorius/items/97cf87d36807d00b883b

anonymous_controller.rb

class AnonymousController < ApplicationController
  def index
    render "#{params[:directory]}/index"
  end
end

file2.txt

mkdir app/views/foo
touch app/views/foo/index.html.erb 

mkdir app/views/bar
touch app/views/bar/index.html.erb 

file3.txt

$ rake routes
Prefix Verb URI Pattern    Controller#Action
   bar GET  /bar(.:format) anonymous#index {:directory=>"bar"}
   foo GET  /foo(.:format) anonymous#index {:directory=>"foo"}

routes.rb

NoControllerApp::Application.routes.draw do
  exclude_dir = ["layouts"]
  anonymous_dir = []
  Dir::glob(File.join(Rails.root.to_s, "/app/views/*/")).map{|f| anonymous_dir << f.split("/").last }

  (anonymous_dir - exclude_dir).each do |dir|
    get "#{dir}" => "anonymous#index", :defaults => {:directory => "#{dir}"}
  end
end