gistfile1.rb

require 'rubygems'
require 'builder'

xml = Builder::XmlMarkup.new

@recent_items = [
  {:title => "Item Title",
    :description => "Item Description",
    :pub_date => Date.today,
    :guid => "10893750189756019760127",
    :link => "http://linky.example.com",
    :author_name => "Mr Sillypants"}
]

output = xml.rss("version" => "2.0", "xmlns:dc" => "http://purl.org/dc/elements/1.1/") do
    xml.channel do
      xml.title("Feed Title")
      xml.link("http://www.example.com")
      xml.description "A silly description"
      xml.language "en-gb"
      xml.ttl "40"

      for item in @recent_items
        xml.item do
          xml.title(item[:title])
          xml.description(item[:description]) if item[:description]
          xml.pubDate(item[:pub_date])
          xml.guid(item[:guid])
          xml.link(item[:link])

          xml.tag!("dc:creator", item[:author_name]) if item[:author_name]
        end
      end
    end
  end
puts output
# >> <rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/"><channel><title>Feed Title</title><link>http://www.example.com</link><description>A silly description</description><language>en-gb</language><ttl>40</ttl><item><title>Item Title</title><description>Item Description</description><pubDate>2009-06-03</pubDate><guid>10893750189756019760127</guid><link>http://linky.example.com</link><dc:creator>Mr Sillypants</dc:creator></item></channel></rss>