How do I write a conditional for whether a section contains entries? I've got a blog section on a page but want to hide it if there are no blogs. 

{% set blog = craft.entries.section('blog').limit(5) %}
{% if blog !='' %}
  &lt;div class="something"&gt;
    {% for entry in blog %}
      ...
    {% endfor %}
  &lt;/div&gt;
{% endif %}
Your blog variable is an ElementCriteriaModel, which can be treated like an iterable array:

{% if blog|length %}
    Content
{% endif %}