functions.php

<li id="camera-brands" class="widget-container">
  <h3 class="widget-title">Camera Brands</h3>
  <?php $cam_brands = get_terms('brands', 'hide_empty=1'); ?>
  <ul>
    <?php foreach( $cam_brands as $brand ) : ?>
      <li>
        <a href="<?php echo get_term_link( $brand->slug, 'brands' ); ?>">
          <?php echo $brand->name; ?>
        </a>
        <ul>
          <?php 
            $wpq = array( 'post_type' => 'cameras', 'taxonomy' => 'brands', 'term' => $brand->slug );
            $brand_posts = new WP_Query ($wpq);
          ?>
          <?php foreach( $brand_posts->posts as $post ) : ?>
            <li>
              <a href="<?php echo get_permalink( $post->ID ); ?>">
                <?php echo $post->post_title; ?>
              </a>
            </li>
          <?php endforeach ?>
        </ul>
      </li>
    <?php endforeach ?>
  </ul>
</li>