drupal_add_feed()

Drupal RSS functionality is spread out, and so is information on it. After first accumulating mental notes, which turned into a collection of written notes and code snippets, I realized there's a lot to be said on the topic. A single overview covering all things RSS seemed like a useful idea. This is a starting point covering many things RSS. I invite you to leave a comment if you have anything to add, a great reference or blog post, or if I've gotten something wrong.

"Out of the box" RSS

• RSS is configured and controlled at Administration > Content management > RSS Publishing
  
  
• The default RSS URL is rss.xml (e.g. www.example.com/rss.xml)
• The default RSS feed selects content using the same selection criteria as the /node path ("/node" is the default front page setting). It contains the content of any node that's both "Published" and "Promoted to front page".
  
  
  
  The exact content and number of nodes is determined by the RSS settings.
• There is no provision to theme a node's RSS output in the PHPTemplate theme engine. Your node.tpl.php file is ignored when the feed content is rendered.
• Because of the above point, double check the RSS feed output of any feed containing nodes you've created or modified with CCK.
• Every taxonomy term automatically gets a feed (whether you want it or not)
• The is no provision in the Drupal base installation (core) to publish comments in a RSS feed. A contributed module (RSS Comments or Views) is required. More on this later on.
• The RSS feed will only be published on the front page. More on this later.