diff --git a/lib/jekyll/page.rb b/lib/jekyll/page.rb
index 2041e4c9..10069f6c 100644
--- a/lib/jekyll/page.rb
+++ b/lib/jekyll/page.rb
@@ -1,7 +1,6 @@
 module Jekyll
   class Page
     include Convertible
-    include URL
 
     attr_writer :dir
     attr_accessor :site, :pager
@@ -63,6 +62,17 @@ module Jekyll
       end
     end
 
+    # The generated relative url of this page. e.g. /about.html.
+    #
+    # Returns the String url.
+    def url
+      @url ||= URL.new({
+        :template => template,
+        :placeholders => url_placeholders,
+        :permalink => permalink
+      }).to_s
+    end
+
     # See url.rb for an explanation
     def url_placeholders
       {
diff --git a/lib/jekyll/post.rb b/lib/jekyll/post.rb
index 79e751fe..6b5c38d5 100644
--- a/lib/jekyll/post.rb
+++ b/lib/jekyll/post.rb
@@ -2,7 +2,6 @@ module Jekyll
   class Post
     include Comparable
     include Convertible
-    include URL
 
     class << self
       attr_accessor :lsi
@@ -195,6 +194,17 @@ module Jekyll
       end
     end
 
+    # The generated relative url of this post.
+    #
+    # Returns the String url.
+    def url
+      @url ||= URL.new({
+        :template => template,
+        :placeholders => url_placeholders,
+        :permalink => permalink
+      }).to_s
+    end
+
     # See url.rb for an explanation
     def url_placeholders
       {
@@ -204,7 +214,7 @@ module Jekyll
         "title"      => CGI.escape(slug),
         "i_day"      => date.strftime("%d").to_i.to_s,
         "i_month"    => date.strftime("%m").to_i.to_s,
-        "categories" => categories.map { |c| URI.escape(c.to_s) }.join('/'),
+        "categories" => (categories || []).map { |c| URI.escape(c.to_s) }.join('/'),
         "short_month" => date.strftime("%b"),
         "y_day"      => date.strftime("%j"),
         "output_ext" => self.output_ext
diff --git a/lib/jekyll/url.rb b/lib/jekyll/url.rb
index fb9f8ee0..383cebaa 100644
--- a/lib/jekyll/url.rb
+++ b/lib/jekyll/url.rb
@@ -1,38 +1,49 @@
-# The URL module provides methods that generate a URL for a resource in which they're
-# included, such as a Post or a Page.
+# Public: Methods that generate a URL for a resource such as a Post or a Page.
 #
-# Requires
+# Examples
 #
-#   self.permalink  - If a permalink is set in the included instance, that permalink
-#                     will be returned instead of any URL that might've been generated
+#   URL.new({
+#     :template => /:categories/:title.html",
+#     :placeholders => {:categories => "ruby", :title => "something"}
+#   }).to_s
 #
-#   self.url_placeholders - Placeholders that may be used in the URL, which will be replaced
-#                         with the values when the URL is generated. Must return a Hash
-#                         mapping placeholder names to their values. For example, if this
-#                         method returned
-#
-#                           { "year" => Time.now.strftime("%Y") }
-#
-#                         Every occurrence of ":year" (note the colon) would be replaced with
-#                         the current year.
-#
-#
-
 module Jekyll
-  module URL
+  class URL
 
-    # The generated relative url of this page. e.g. /about.html.
-    #
-    # Returns the String url.
-    def url
-      @url ||= sanitize_url(permalink || generate_url)
+    # options - One of :permalink or :template must be supplied.
+    #           :template     - The String used as template for URL generation,
+    #                           for example "/:path/:basename:output_ext", where
+    #                           a placeholder is prefixed with a colon.
+    #           :placeholders - A hash containing the placeholders which will be
+    #                           replaced when used inside the template. E.g.
+    #                           { "year" => Time.now.strftime("%Y") } would replace
+    #                           the placeholder ":year" with the current year.
+    #           :permalink    - If supplied, no URL will be generated from the
+    #                           template. Instead, the given permalink will be
+    #                           used as URL.
+    def initialize(options)
+      @template = options[:template]
+      @placeholders = options[:placeholders] || {}
+      @permalink = options[:permalink]
+
+      if (@template || @permalink).nil?
+        raise ArgumentError, "One of :template or :permalink must be supplied."
+      end
     end
 
-    # Generate the URL by replacing all placeholders with their respective values
+    # The generated relative URL of the resource
+    #
+    # Returns the String URL
+    def to_s
+      sanitize_url(@permalink || generate_url)
+    end
+
+    # Internal: Generate the URL by replacing all placeholders with their
+    # respective values
     #
     # Returns the _unsanitizied_ String URL
     def generate_url
-      url_placeholders.inject(template) { |result, token|
+      @placeholders.inject(@template) { |result, token|
         result.gsub(/:#{token.first}/, token.last)
       }
     end
diff --git a/test/test_url.rb b/test/test_url.rb
new file mode 100644
index 00000000..0576eda2
--- /dev/null
+++ b/test/test_url.rb
@@ -0,0 +1,28 @@
+require 'helper'
+
+class TestURL < Test::Unit::TestCase
+  context "The URL class" do
+
+    should "throw an exception if neither permalink or template is specified" do
+      assert_raises ArgumentError do
+        URL.new(:placeholders => {})
+      end
+    end
+
+    should "replace placeholders in templates" do
+      assert_equal "/foo/bar", URL.new(
+        :template => "/:x/:y",
+        :placeholders => {:x => "foo", :y => "bar"}
+      ).to_s
+    end
+
+    should "return permalink if given" do
+      assert_equal "/le/perma/link", URL.new(
+        :template => "/:x/:y",
+        :placeholders => {:x => "foo", :y => "bar"},
+        :permalink => "/le/perma/link"
+      ).to_s
+    end
+
+  end
+end