_products.html.erb

<tbody>
  <% products.each do |product| %>
    <tr>
      <td><%= link_to product.name, product %></td>
      <td><%= truncate(strip_tags(product.description), :length => 80) %></td>
      <td><%= product.price %></td>
    </tr>
  <% end %>
</tbody>

categories_controller.rb

class CategoriesController < ApplicationController
  before_filter :set_categories, :only => [ :index, :show ]

  def index
  end

  def show
    @category = Category.find(params[:id])
    @title = @category.name
  end

  def new
    @category = Category.new
    @title = "Add Category"
  end

  def create
    @category = Category.new(params[:category])
    if @category.save
      redirect_to @category
    else
      @title = "Add category"
      render 'new'
    end
  end

  protected

  def set_categories
    @categories = Category.all
  end
end

show.html.erb

<div class="span-6">
  <%= render :partial => "index" %>
</div>

<div class="span-18 last">
  <% unless @category.products.empty? %>
    <table>
      <thead>
         <tr>
          <th>Product name</th>
          <th>Description</th>
          <th>Price</th>
        </tr>
      </thead>
      <%= render :partial => "products", :locals => { :products => @category.products } %>
    </table>
  <% end %>
</div>