game.rb

#added this method to Game model

#To see more about reading and writing csv files, see http://fastercsv.rubyforge.org/
def self.convert_games_to_csv(games)
  require 'fastercsv' #<= This require statement really belongs at the top of the config/environment.rb file
  csv = ['home team', 'away team', 'home scroe', 'away score'].to_csv
  games.each do |game|
    csv << [game.home_team.name, game.away_team.name, game.home_score, game.away_score].to_csv
  end
  csv
end

games_controller.rb

#modified this index action in the games controller

def index
  @games = Game.all
  respond_to do |format|
    format.html
    format.csv do
      #see also send_file (http://railsbrain.com/api/rails-2.3.2/doc/index.html?a=M000195&name=send_file)
      send_data Game.convert_games_to_csv(@games), :filename => 'games.csv'
    end
    format.xml do
      render :xml => @games.to_xml
    end
  end
end

games_index.html.erb

<% #Added this link to the games index view %>
<li><%= link_to 'Export Games', games_path(:format => :csv) %></li>