tag_cloud_tag.rb

module Jekyll
  class TagCloudTag < Liquid::Tag
    safe = true
    
    def initialize(tag_name, text, tokens)
      super
    end

    def render(context)
      html = ""
      tags = context.registers[:site].tags
      avg = tags.inject(0.0) {|memo, tag| memo += tag[1].length} / tags.length
      weights = Hash.new
      tags.each {|tag| weights[tag[0]] = tag[1].length/avg}
      tags.each do |tag, posts|
        html << "<span style='font-size: #{sprintf("%d", weights[tag] * 100)}%'><a href='/tags/#{tag}/'>#{tag}</a></span>\n"
      end
      html
    end
  end
end

Liquid::Template.register_tag('tag_cloud', Jekyll::TagCloudTag)

tag_page.rb

module Jekyll
  class TagPage
    include Convertible
    attr_accessor :site, :pager, :name, :ext
    attr_accessor :basename, :dir, :data, :content, :output

    def initialize(site, tag, posts)
      @site = site
      @tag = tag
      self.ext = '.html'
      self.basename = 'index'
      self.content = <<-EOS
{% for post in page.posts %}
<h3>{{ post.date | date: "%A %d.%m." }} &mdash; <a href="{{ post.url }}">{{ post.title }}</a></h3>

<p>{{ post.content | truncatewords: 20 }}</p>

<p>
{% if post.categories != empty %}
In {{ post.categories | array_to_sentence_string }}.
{% endif %}
{% if post.tags != empty %}
Tagged {{ post.tags | array_to_sentence_string }}.
</p>
{% endif %}
{% endfor %}
EOS
      self.data = {
        'layout' => 'default',
        'type' => 'tag',
        'title' => "Posts tagged #{@tag}",
        'posts' => posts
      }
    end

    def render(layouts, site_payload)
      payload = {
        "page" => self.to_liquid,
        "paginator" => pager.to_liquid
      }.deep_merge(site_payload)
      do_layout(payload, layouts)
    end

    def url
      File.join("/tags", @tag, "index.html")
    end

    def to_liquid
      self.data.deep_merge({
                             "url" => self.url,
                             "content" => self.content
                           })
    end

    def write(dest_prefix, dest_suffix = nil)
      dest = dest_prefix
      dest = File.join(dest, dest_suffix) if dest_suffix
      path = File.join(dest, CGI.unescape(self.url))
      FileUtils.mkdir_p(File.dirname(path))
      File.open(path, 'w') do |f|
        f.write(self.output)
      end
    end

    def html?
      true
    end
  end
end

tag_page_generator.rb

module Jekyll
  class TagPageGenerator < Generator
    safe true

    def generate(site)
      site.tags.each do |tag, posts|
        site.pages << TagPage.new(site, tag, posts)
      end
    end
  end
end