It’s often useful, for example on a staff page showing bios, to show subpage content on the parent page. This way a sub-page can be created for a staff member and all staff can then be featured on the main page. This technique can work just as well for products or projects. The code snippet I use looks like this:

<?php if(_is_child())
 $pages = get_pages('child_of='.$post->ID.'
&sort_column=menu_order&sort_order=asc&parent='.$post->ID);
 foreach($pages as $page) { ?>
 <div id="<?php echo $page->post_name; ?>">
 <h3><?php echo $page->post_title ?></h3>
 <?php echo $page->post_content; ?>
</div>
<?php } ?>

I use if(_is_child()) to restrict this feature to second-level child pages so that only third-level grandchild pages are shown.