The usage of Plan's Atom feed generator, based on Rails' atom_feed Builder handler. It works by generating SXML which is then turned into the actual XML of the feed.

gistfile1.sls

(atom-feed
  (title "David's Weblog")
  (subtitle "An awesome weblog")
  (link 'self "http://dpk.org.uk/feed/")
  
  (each post (posts 20)
    (entry
      (title (post 'title)) ; maybe do an automagic thing to detect dictionary items with the same name as atom properties?
      (id (tag-uri post))
      (link 'alternate (post 'permalink)) ; could be automagic, too
      (published (post 'pub-date)) ; automagic?
      (updated   (post 'upd-date)) ;     "    ?
      (author '(name "David Kendal"))
      (content (post 'body)))))