How to display subcategories on category page?

Use below code

$_category = Mage::registry('current_category');

$subcategories = Mage::getModel('catalog/category')->getCategories($_category->getId());


foreach ($subcategories as $subcategory){ ?>
    <li><a href="<?php echo $subcategory->getUrl() ?>"><?php echo $subcategory->getName() ?></a></li>
<?php }

Try to make a var dump of "$_subcat" inside the foreach:

<?php foreach ($this->getCurrentCategory()->getChildrenCategories() as $_subcat): ?>
    <?php var_dump($_subcat->getData()); die(); ?>
<?php endforeach ?>

You will display all the options available to use.