Rails markdown parser using Redcarpet. It also parses erb within the markdown template.

redcarpet.rb

# gem install redcarpet
# config/initializers/redcarpet.rb
# {viewname}.html.md

module ActionView
  class Template
    module Handlers
      class Markdown
        class_attribute :default_format
        self.default_format = Mime::HTML

        def call(template)
          erb = ActionView::Template.registered_template_handler(:erb)
          source = erb.call(template)
          <<-SOURCE
            markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML,
                                          :autolink => true,
                                          :space_after_headers => true,
                                          :fenced_code_blocks => true)
            markdown.render(begin;#{source};end).html_safe
          SOURCE
        end
      end
    end

    register_template_handler(:md, ActionView::Template::Handlers::Markdown.new)
    register_template_handler(:mdown, ActionView::Template::Handlers::Markdown.new)
    register_template_handler(:markdown, ActionView::Template::Handlers::Markdown.new)
  end
end