Provides a {% lead %} block to define lead-in text. Adds text inside block to post data's 'lead' field and wraps text inside a paragraph with a style class for customisation.

aether_lead-in_block.rb

# Title: Lead-in Text Block
# Author: Yetrina Battad (http://aether.nu)
# Description: Provides a block for lead-in text. Inspired by this plugin: http://blog.darkrefraction.com/2012/jekyll-excerpt-plugin.html
#
# Captures the text between the 'lead' block and places it in the post data's 'lead' property.
# Also wraps the text between the 'lead' tags into a paragraph with CSS hook for styling.
#
# Usage:
#   {% lead %}
#   Wheeee!
#   {% endlead %}
#
require 'nokogiri'
require 'rdiscount'

module Jekyll

  class AetherLeadIn < Liquid::Block

    def render(context)
      id = context["page"]["id"]
      site = context.registers[:site]
      output = ''
      site.posts.each do |post|
        if post.id && post.id == id
          post.data["lead"] = super
          break
        end
      end

      html = RDiscount.new(super).to_html
      paragraphize(html)
    end

    def paragraphize(input)
      "<p class=\"lead\">#{input.strip_html_tags(false)}</p>"
    end
  end
end

Liquid::Template.register_tag('lead', Jekyll::AetherLeadIn)