- layout
<div id="base">
   <%= link_to "Ajax!", remote: true, class: "getUsers" %>
    <div class="wrapper"></div>
</div>

- controller
class UsersController < ApplicationController
  layout false

  def index
    @users = User.all
  end
end

- view
<div id="userCtrl">
  <ul>
    <% @users.each do |u| %>
        <li><%= u.name %></li>
     <% end %>
  </ul>
</div>

- css
#userCtrl {
  # CSS for userCtrl
}

- js
$(function() {
  $(document).on("ajax:success", '#userCtrl .getUsers', function(q, data, xhr){
    $("#base .wrapper").html(data);
  });
});