Use this code to manually sort posts with Jekyll, using Liquid only.

2014-01-01-post-2.md

layout	post
weight	1
title	Title
description	This is a post!

Even though this post is much older than the other, it will appear first in the post list! Magic! Witchcraft!

2014-03-01-post.md

layout	post
weight	2
title	Title
description	This is a post!

This post is more recent than the other, but it will appear second in the post list! Wowza!

index.html

{% for weight in (1..20) %}
  {% for post in site.posts %}
    {% if post.weight == weight %}
      {% if post.categories contains 'work' %}
        <a href="{{ post.url }}">{{ post.title }}</a>
      {% endif %}
    {% endif %}
  {% endfor %}
{% endfor %}