@briantist is right, you need to dig into the site.tags collection.
, Jekyll .
(: ruby.html) include, ruby:
---
layout: page
title: Ruby
---
{% include tagPagesLoop.html tagName='ruby' %}
_includes/tagPagesLoop.html
<h2>All {{ include.tagName }} posts</h2>
{% for post in site.tags[include.tagName] %}
<h3>{{ post.title }}</h3>
other stuff here
{% endfor %}
, , , .