user.company fails to load anything...

company.rb

class Company < ActiveRecord::Base
  attr_accessible :address, :city, :contact_email, :contact_name, :fax_number, :name, :phone_number, :state, :zip
  has_many :users
end

class User < ActiveRecord::Base
  attr_accessible :company_id, :email, :enabled, :first_name, :last_name, :password, :username
  belongs_to :company
end

class UsersController < ApplicationController
  # GET /users
  # GET /users.json
  def index
    @users = User.all

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @users }
    end
  end
end

<% @users.each do |user| %>
  <tr>
    <td><%= user.username %></td>
    <td><%= user.email %></td>
    <td><%= user.first_name %></td>
    <td><%= user.last_name %></td>
    <td><%= user.company %></td>
    <td><%= user.enabled %></td>
    <td><%= link_to 'Show', user %></td>
    <td><%= link_to 'Edit', edit_user_path(user) %></td>
    <td><%= link_to 'Destroy', user, method: :delete, data: { confirm: 'Are you sure?' } %></td>
  </tr>
<% end %>

class CreateCompanies < ActiveRecord::Migration
  def change
    create_table :companies do |t|
      t.string :name
      t.string :phone_number
      t.string :fax_number
      t.string :address
      t.string :city
      t.string :state
      t.string :zip
      t.string :contact_name
      t.string :contact_email

      t.timestamps
    end
  end
end

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string :username
      t.string :email
      t.string :first_name
      t.string :last_name
      t.integer :company_id
      t.string :password
      t.integer :enabled

      t.timestamps
    end
  end
end

You need to access to an attribute of the company class:

 <td><%= user.company.name %></td>