<ul>
<?php
$field = get_post_meta($post->ID, 'field', true);
$items = explode("\n",$field);
foreach ($items as $item) {
echo '<li>'.$item.'</li>';
}
?>
</ul>
This bit of code would basically separate line breaks on a textarea custom field into li tags. Obviosly, we would need to create a custom field for this to work. Change field to whatever your custom field key may be.