If you like Atom more than RSS use the atom_feed_helper.

Here’s the template, modify it to fit your needs. I know there are plugins and other ways of doing this, but I hate code that gets too abstract:

   1  <?xml version="1.0"?>
   2  <rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
   3    <channel>
   4      <atom:link href="http://xxxxxxx" rel="self" type="application/rss+xml" />
   5      <title>Code Snippets - Aktagon</title>
   6      <link>http://snippets.aktagon.com/</link>
   7      <description>Share your code with the world. Allow others to review and comment.</description>
   8      <language>en-us</language>
   9      <pubDate><%= @snippets[0].created_at.rfc822 %></pubDate>
  10      <lastBuildDate><%= @snippets[0].created_at.rfc822 %></lastBuildDate>
  11      <docs>http://blogs.law.harvard.edu/tech/rss</docs>
  12      <generator>Aktagon Snippets</generator>
  13   <% for snippet in @snippets %>
  14      <item>
  15        <title><![CDATA[<%= snippet.title %>]]></title>
  16        <link><%= snippet_url(snippet) %></link>
  17        <description><![CDATA[<%= snippet.rendered_body %>]]></description>
  18        <pubDate><%= @snippets[0].created_at.rfc822 %></pubDate>
  19        <guid><%= snippet_url(snippet) %></guid>
  20  	  <% for tag in snippet.tags%>
  21  		<category domain="http://snippets.aktagon.com/snippets"><![CDATA[<%= tag.name %>]]></category>
  22  	  <% end%>
  23      </item>
  24  <% end %>
  25    </channel>
  26  </rss>
  27  

Remember to serve the feed with the correct HTTP headers.

It also helps to have an auto-discovery tag inside the head tag:

   1  <link rel="alternate" type="application/rss+xml" title="RSS feed" href="http://<%= request.host %>/rss/" />