feed.rb#refresh

  def self.refresh
    feeds = self.active

    feeds.each do |feed|
      doc = Nokogiri::XML(open(feed.url))

      doc.css('item').each do |item|
        hash = Digest::SHA1.hexdigest item

        unless Item.find_by_salt hash
          feed.items.create :source => item.to_xml, :salt => hash
        end
      end
    end
  end

Flickr XML

<rss xmlns:media="http://search.yahoo.com/mrss/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:flickr="urn:flickr:" version="2.0">
	<channel>


		<title>Matthew Anderson's favorites</title>
		<link>http://www.flickr.com/photos/matthew-anderson/favorites/</link>
 		<description>Matthew Anderson's favorites on Flickr.</description>
		<pubDate>Wed, 26 Aug 2009 13:51:28 -0700</pubDate>
		<lastBuildDate>Wed, 26 Aug 2009 13:51:28 -0700</lastBuildDate>
		<generator>http://www.flickr.com/</generator>
		<image>
			<url/>
			<title>Matthew Anderson's favorites</title>
			<link>http://www.flickr.com/photos/matthew-anderson/favorites/</link>
		</image>

		<item>
			<title>NYC Type - 21 Air-26 - NoHo</title>
			<link>http://www.flickr.com/photos/ampersanderson/3859529839/</link>
			<description>&lt;p&gt;&lt;a href="http://www.flickr.com/people/ampersanderson/"&gt;ampersanderson&lt;/a&gt; posted a photo:&lt;/p&gt;
&lt;p&gt;&lt;a href="http://www.flickr.com/photos/ampersanderson/3859529839/" title="NYC Type - 21 Air-26 - NoHo"&gt;&lt;img src="http://farm3.static.flickr.com/2471/3859529839_61f0417e05_m.jpg" width="240" height="182" alt="NYC Type - 21 Air-26 - NoHo" /&gt;&lt;/a&gt;&lt;/p&gt;

</description>
			<pubDate>Wed, 26 Aug 2009 13:51:28 -0700</pubDate>
			                        <dc:date.Taken>2009-08-26T16:51:28-08:00</dc:date.Taken>
            			<author flickr:profile="http://www.flickr.com/people/ampersanderson/">nobody@flickr.com (ampersanderson)</author>
			<guid isPermaLink="false">tag:flickr.com,2004:/photo/3859529839/</guid>
                            			<media:content url="http://farm3.static.flickr.com/2471/3859529839_9cb492ecd6_o.jpg" type="image/jpeg" height="607" width="800"/>
            <media:title>NYC Type - 21 Air-26 - NoHo</media:title>
        <media:thumbnail url="http://farm3.static.flickr.com/2471/3859529839_61f0417e05_s.jpg" height="75" width="75"/>
        <media:credit role="photographer">ampersanderson</media:credit>


		</item>

YouTube XML

<feed xmlns="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns:openSearch="http://a9.com/-/spec/opensearch/1.1/" xmlns:gd="http://schemas.google.com/g/2005" gd:etag="W/&quot;Ak8MQXw9fip7ImA9WxNSE0g.&quot;">
  <id>tag:youtube.com,2008:user:WanderingMatt:favorites</id>
  <updated>2009-08-27T07:41:20.266Z</updated>
  <category scheme="http://schemas.google.com/g/2005#kind" term="http://gdata.youtube.com/schemas/2007#favorite"/>
  <title>Favorites of WanderingMatt</title>
  <logo>http://www.youtube.com/img/pic_youtubelogo_123x63.gif</logo>
  <link rel="related" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/users/wanderingmatt?client=ytapi-youtube-user&amp;v=2"/>
  <link rel="alternate" type="text/html" href="http://www.youtube.com/profile_favorites?user=WanderingMatt"/>
  <link rel="http://schemas.google.com/g/2005#feed" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/users/WanderingMatt/favorites?client=ytapi-youtube-user&amp;v=2"/>
  <link rel="http://schemas.google.com/g/2005#batch" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/users/WanderingMatt/favorites/batch?client=ytapi-youtube-user&amp;v=2"/>
  <link rel="self" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/users/WanderingMatt/favorites?start-index=1&amp;max-results=25&amp;client=ytapi-youtube-user&amp;v=2"/>
  <link rel="service" type="application/atomsvc+xml" href="http://gdata.youtube.com/feeds/base/users/WanderingMatt/favorites?alt=atom-service&amp;v=2"/>
  <author>
    <name>WanderingMatt</name>
    <uri>http://gdata.youtube.com/feeds/base/users/wanderingmatt</uri>
  </author>
  <generator version="2.0" uri="http://gdata.youtube.com/">YouTube data API</generator>
  <openSearch:totalResults>7</openSearch:totalResults>
  <openSearch:startIndex>1</openSearch:startIndex>
  <openSearch:itemsPerPage>25</openSearch:itemsPerPage>
  <entry gd:etag="W/&quot;AkAEQH47eCp7ImA9WxNSE0g.&quot;">
    <id>tag:youtube.com,2008:favorite:vjVQa1PpcFO-tj1IT50VcuFmA_c66pQmNiO0eVBdH-Y</id>
    <published>2009-08-27T07:38:21.000Z</published>
    <updated>2009-08-27T07:38:21.000Z</updated>
    <category scheme="http://schemas.google.com/g/2005#kind" term="http://gdata.youtube.com/schemas/2007#favorite"/>
    <title>Starcraft 2 - Wings of Liberty Preview - HD</title>
    <link rel="alternate" type="text/html" href="http://www.youtube.com/watch?v=Y-9Ms9Jr9jQ"/>
    <link rel="related" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/videos/Y-9Ms9Jr9jQ?client=ytapi-youtube-user&amp;v=2"/>
    <link rel="self" type="application/atom+xml" href="http://gdata.youtube.com/feeds/base/users/WanderingMatt/favorites/vjVQa1PpcFO-tj1IT50VcuFmA_c66pQmNiO0eVBdH-Y?client=ytapi-youtube-user&amp;v=2"/>
    <author>
      <name>WanderingMatt</name>
      <uri>http://gdata.youtube.com/feeds/base/users/wanderingmatt</uri>
    </author>
  </entry>