1. 新建插件文件plugins/category_list_tag.rb, 内容如下:

module Jekyll  
  class CategoryListTag < Liquid::Tag  
    def render(context)  
      html = ""  
      categories = context.registers[:site].categories.keys  
      categories.sort.each do |category|  
        posts_in_category = context.registers[:site].categories[category].size  
        category_dir = context.registers[:site].config['category_dir']  
        category_url = File.join(category_dir, category.gsub(/_|\P{Word}/, '-').gsub(/-{2,}/, '-').downcase)  
        html << "<li class='category'><a href='/#{category_url}/'>#{category} (#{posts_in_category})</a></li>\n"  
      end  
      html  
    end  
  end  
end  

Liquid::Template.register_tag('category_list', Jekyll::CategoryListTag)  

2. 新建source/_includes/asides/category_list.html文件，内容如下：

<section>  
  <h1>Categories</h1>  
  <ul id="categories">  
    { % category_list % }  
  </ul>  
</section>  

3. 修改_config.yml文件，在default_asides项中添加asides/category_list.html, 值之间以逗号隔开:

default_asides:[asides/category_list.html, asides/recent_posts.html, ...]  

4. rake generate; rake preview; rake deploy;

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参考资料：

http://www.cnblogs.com/oec2003/archive/2013/05/31/3109577.html