diff --git a/lib/jekyll/site.rb b/lib/jekyll/site.rb
index 97b7b677..e171d090 100644
--- a/lib/jekyll/site.rb
+++ b/lib/jekyll/site.rb
@@ -2,7 +2,7 @@ module Jekyll
   
   class Site
     attr_accessor :source, :dest
-    attr_accessor :layouts, :posts
+    attr_accessor :layouts, :posts, :categories
     
     # Initialize the site
     #   +source+ is String path to the source directory containing
@@ -16,6 +16,7 @@ module Jekyll
       self.dest = dest
       self.layouts = {}
       self.posts = []
+      self.categories = Hash.new { |hash, key| hash[key] = Array.new }
     end
     
     # Do the actual work of processing the site and generating the
@@ -63,6 +64,7 @@ module Jekyll
         if Post.valid?(f)
           post = Post.new(self.source, dir, f)
           self.posts << post
+          post.categories.each { |c| self.categories[c] << post }
         end
       end
       
@@ -72,6 +74,7 @@ module Jekyll
       end
       
       self.posts.sort!
+      self.categories.values.map { |cats| cats.sort! { |a, b| b <=> a} }
     rescue Errno::ENOENT => e
       # ignore missing layout dir
     end
diff --git a/test/source/foo/_posts/bar/2008-12-12-topical-post.textile b/test/source/foo/_posts/bar/2008-12-12-topical-post.textile
new file mode 100644
index 00000000..813db112
--- /dev/null
+++ b/test/source/foo/_posts/bar/2008-12-12-topical-post.textile
@@ -0,0 +1,8 @@
+---
+layout: default
+title: Topical Post
+---
+
+h1. {{ page.title }}
+
+This post has a topic.
diff --git a/test/test_post.rb b/test/test_post.rb
index 9ff73bae..713eec02 100644
--- a/test/test_post.rb
+++ b/test/test_post.rb
@@ -96,6 +96,12 @@ class TestPost < Test::Unit::TestCase
     assert_equal "<<< <p>url: /2008/11/21/complex.html<br />\ndate: #{Time.parse("2008-11-21")}<br />\nid: /2008/11/21/complex</p> >>>", p.output
   end
   
+  def test_categories_and_topics
+    p = Post.new(File.join(File.dirname(__FILE__), *%w[source]), 'foo', 'bar/2008-12-12-topical-post.textile')
+    assert_equal ['foo'], p.categories
+    assert_equal ['bar'], p.topics
+  end    
+  
   def test_include
     Jekyll.source = File.join(File.dirname(__FILE__), *%w[source])
     p = Post.new(File.join(File.dirname(__FILE__), *%w[source]), '', "2008-12-13-include.markdown")
diff --git a/test/test_site.rb b/test/test_site.rb
index 52c1ca83..fa256177 100644
--- a/test/test_site.rb
+++ b/test/test_site.rb
@@ -22,9 +22,12 @@ class TestSite < Test::Unit::TestCase
     assert_equal 4, @s.posts.size
   end
   
-  def test_write_posts
+  def test_site_payload
     clear_dest
-    
     @s.process
+    
+    assert_equal 5, @s.posts.length
+    assert_equal ['foo'], @s.categories.keys
+    assert_equal 1, @s.categories['foo'].length
   end
 end