Sorted navigation menu with Jekyll and Liquid

Since Jekyll 2.2.0 you can sort an array of objects by any object property. You can now do :

{% assign pages = site.pages | sort:"weight"  %}
<ul>
  {% for p in pages %}
    <li>
      <a {% if p.url == page.url %}class="active"{% endif %} href="https://stackoverflow.com/questions/9053066/{{ p.url }}">
        {{ p.title }}
      </a>
    </li>
  {% endfor %}
</ul>

And save a lot of build time compared to @kikito solution.

edit:
You MUST assign your sorting property as an integer weight: 10 and not as a string weight: "10".

Assigning sorting properties as string will ends up in a a string sort like “1, 10, 11, 2, 20, …”