application.js

jQuery(function() {
    $("iframe[data-url^='http']").attr("src", function() { return $(this).attr("data-url") });
});

application_helper.rb

module ApplicationHelper
  # Facebook Like button
  def like_button_tag(url)
    content_tag :iframe, nil, { :'data-url' => "http://www.facebook.com/plugins/like.php?href=#{URI::escape(url)}&layout=standard&show_faces=false&width=400&action=like&colorscheme=light&height=35", 
                               :scrolling => "no", 
                               :frameborder => "0", 
                               :style => "border:none; overflow:hidden; width:400px; height:35px;", 
                               :allowTransparency => "true" }
  end

  # Tweet button
  def tweet_button_tag(options = {})
    src = "http://platform.twitter.com/widgets/tweet_button.html?via=YOUR_TWITTER_ACCOUNT&count=horizontal"
    src << "&text=#{URI::escape(options[:tweet_text])}" if options[:tweet_text]
    
    content_tag :iframe, nil, { :'data-url' => src, 
                                :scrolling => "no", 
                                :frameborder => "0", 
                                :style => "width:130px; height:50px;",
                                :allowTransparency => "true" }
  end
end