diff --git a/README.md b/README.md
index cd6bb94a..cb4d7395 100644
--- a/README.md
+++ b/README.md
@@ -80,8 +80,8 @@ choose. Special footers can be created in `footer files`. Other content
 ## PAGE FILES
 
 Page files may be written in any format supported by
-[GitHub-Markup](http://github.com/github/markup) (except roff). The
-current list of formats and allowed extensions is:
+[GitHub-Markup](http://github.com/github/markup) (except roff). By default,
+Gollum recognizes the following extensions:
 
 * ASCIIDoc: .asciidoc
 * Creole: .creole
@@ -93,8 +93,14 @@ current list of formats and allowed extensions is:
 * Textile: .textile
 * MediaWiki: .mediawiki, .wiki
 
+You may also register your own extensions and parsers:
+
+    Gollum::Markup.register(:angry, "Angry") do |content|
+      content.upcase
+    end
+
 Gollum detects the page file format via the extension, so files must have one
-of the supported extensions in order to be converted.
+of the default or registered extensions in order to be converted.
 
 Page file names may contain any printable UTF-8 character except space
 (U+0020) and forward slash (U+002F). If you commit a page file with any of
diff --git a/lib/gollum.rb b/lib/gollum.rb
index e4d33d31..b1eec708 100644
--- a/lib/gollum.rb
+++ b/lib/gollum.rb
@@ -19,6 +19,7 @@ require File.expand_path('../gollum/page', __FILE__)
 require File.expand_path('../gollum/file', __FILE__)
 require File.expand_path('../gollum/file_view', __FILE__)
 require File.expand_path('../gollum/markup', __FILE__)
+require File.expand_path('../gollum/markups', __FILE__)
 require File.expand_path('../gollum/sanitization', __FILE__)
 require File.expand_path('../gollum/web_sequence_diagram', __FILE__)
 require File.expand_path('../gollum/frontend/uri_encode_component', __FILE__)
diff --git a/lib/gollum/frontend/views/editable.rb b/lib/gollum/frontend/views/editable.rb
index 6f9ac51b..365573ad 100644
--- a/lib/gollum/frontend/views/editable.rb
+++ b/lib/gollum/frontend/views/editable.rb
@@ -1,8 +1,8 @@
 module Precious
   module Editable
     def formats(selected = @page.format)
-      Gollum::Page::FORMAT_NAMES.map do |key, val|
-        { :name     => val,
+      Gollum::Markup.formats.map do |key, val|
+        { :name     => val[:name],
           :id       => key.to_s,
           :selected => selected == key}
       end.sort do |a, b|
diff --git a/lib/gollum/markup.rb b/lib/gollum/markup.rb
index 6d69a9e2..1df5df15 100644
--- a/lib/gollum/markup.rb
+++ b/lib/gollum/markup.rb
@@ -15,6 +15,28 @@ module Gollum
   class Markup
     include Precious::Helpers
 
+    @formats = {}
+
+    class << self
+      attr_reader :formats
+
+      # Register a file extension and associated markup type
+      #
+      # ext     - The file extension
+      # name    - The name of the markup type
+      # options - Hash of options:
+      #           regexp - Regexp to match against.
+      #                    Defaults to exact match of ext.
+      #
+      # If given a block, that block will be registered with GitHub::Markup to
+      # render any matching pages
+      def register(ext, name, options = {}, &block)
+        regexp = options[:regexp] || Regexp.new(ext.to_s)
+        @formats[ext] = { :name => name, :regexp => regexp }
+        GitHub::Markup.add_markup(regexp, &block) if block_given?
+      end
+    end
+
     attr_accessor :toc
     attr_reader   :metadata
 
diff --git a/lib/gollum/markups.rb b/lib/gollum/markups.rb
new file mode 100644
index 00000000..53f45ed3
--- /dev/null
+++ b/lib/gollum/markups.rb
@@ -0,0 +1,13 @@
+module Gollum
+  class Markup
+    register(:markdown,  "Markdown", :regexp => /md|mkdn?|mdown|markdown/)
+    register(:textile,   "Textile")
+    register(:rdoc,      "RDoc")
+    register(:org,       "Org-mode")
+    register(:creole,    "Creole")
+    register(:rest,      "reStructuredText", :regexp => /re?st(\.txt)?/)
+    register(:asciidoc,  "AsciiDoc")
+    register(:mediawiki, "MediaWiki", :regexp => /(media)?wiki/)
+    register(:pod,       "Pod")
+  end
+end
\ No newline at end of file
diff --git a/lib/gollum/page.rb b/lib/gollum/page.rb
index 9a295158..2106ed42 100644
--- a/lib/gollum/page.rb
+++ b/lib/gollum/page.rb
@@ -5,17 +5,6 @@ module Gollum
 
     Wiki.page_class = self
 
-    VALID_PAGE_RE = /^(.+)\.(md|mkdn?|mdown|markdown|textile|rdoc|org|creole|re?st(\.txt)?|asciidoc|pod|(media)?wiki)$/i
-    FORMAT_NAMES = { :markdown  => "Markdown",
-                     :textile   => "Textile",
-                     :rdoc      => "RDoc",
-                     :org       => "Org-mode",
-                     :creole    => "Creole",
-                     :rest      => "reStructuredText",
-                     :asciidoc  => "AsciiDoc",
-                     :mediawiki => "MediaWiki",
-                     :pod       => "Pod" }
-
     # Sets a Boolean determing whether this page is a historical version.
     #
     # Returns nothing.
@@ -26,13 +15,29 @@ module Gollum
     # Returns a Page
     attr_accessor :parent_page
 
-    # Checks if a filename has a valid extension understood by GitHub::Markup.
+
+    # Checks a filename against the registered markup extensions
+    #
+    # filename - String filename, like "Home.md"
+    #
+    # Returns e.g. ["Home", :markdown], or [] if the extension is unregistered
+    def self.parse_filename(filename)
+      return [] unless filename =~ /^(.+)\.([a-zA-Z]\w*)$/i
+      pref, ext = $1, $2
+
+      Gollum::Markup.formats.each_pair do |name, format|
+        return [pref, name] if ext =~ format[:regexp]
+      end
+      []
+    end
+
+    # Checks if a filename has a valid, registered extension
     #
     # filename - String filename, like "Home.md".
     #
     # Returns the matching String basename of the file without the extension.
     def self.valid_filename?(filename)
-      filename && filename.to_s =~ VALID_PAGE_RE && $1
+      self.parse_filename(filename).first
     end
 
     # Checks if a filename has a valid extension understood by GitHub::Markup.
@@ -51,34 +56,9 @@ module Gollum
     #
     # filename - The String filename.
     #
-    # Returns the Symbol format of the page. One of:
-    #   [ :markdown | :textile | :rdoc | :org | :rest | :asciidoc | :pod |
-    #     :roff ]
+    # Returns the Symbol format of the page; one of the registered format types
     def self.format_for(filename)
-      case filename.to_s
-        when /\.(md|mkdn?|mdown|markdown)$/i
-          :markdown
-        when /\.(textile)$/i
-          :textile
-        when /\.(rdoc)$/i
-          :rdoc
-        when /\.(org)$/i
-          :org
-        when /\.(creole)$/i
-          :creole
-        when /\.(re?st(\.txt)?)$/i
-          :rest
-        when /\.(asciidoc)$/i
-          :asciidoc
-        when /\.(pod)$/i
-          :pod
-        when /\.(\d)$/i
-          :roff
-        when /\.(media)?wiki$/i
-          :mediawiki
-        else
-          nil
-      end
+      self.parse_filename(filename).last
     end
 
     # Reusable filter to turn a filename (without path) into a canonical name.
@@ -249,9 +229,7 @@ module Gollum
 
     # Public: The format of the page.
     #
-    # Returns the Symbol format of the page. One of:
-    #   [ :markdown | :textile | :rdoc | :org | :rest | :asciidoc | :pod |
-    #     :roff ]
+    # Returns the Symbol format of the page; one of the registered format types
     def format
       self.class.format_for(@blob.name)
     end
@@ -359,17 +337,7 @@ module Gollum
     #
     # Returns the String extension (no leading period).
     def self.format_to_ext(format)
-      case format
-        when :markdown  then 'md'
-        when :textile   then 'textile'
-        when :rdoc      then 'rdoc'
-        when :org       then 'org'
-        when :creole    then 'creole'
-        when :rest      then 'rest'
-        when :asciidoc  then 'asciidoc'
-        when :pod       then 'pod'
-        when :mediawiki then 'mediawiki'
-      end
+      format == :markdown ? "md" : format.to_s
     end
 
     #########################################################################