In this article I'm writing code for display top level categories and sub categories of current category. If you want to have a list with the sub categories of magento of the current Parent category then you can use below code:-
<?php $_helper = Mage::helper('catalog/category') ?> <?php $_categories = $_helper->getStoreCategories() ?> <?php $currentCategory = Mage::registry('current_category') ?> <?php if (count($_categories) > 0): ?> <ul class="category"> <?php foreach($_categories as $_category): ?> <li> <a href="<?php echo $_helper->getCategoryUrl($_category) ?>"> <?php echo $_category->getName() ?> </a> <?php if ($currentCategory->getId() && $currentCategory->getId() == $_category->getId()): ?> <?php $_category = Mage::getModel('catalog/category')->load($_category->getId()) ?> <?php $_subcategories = $_category->getChildrenCategories() ?> <?php if (count($_subcategories) > 0): ?> <ul class="subcategory"> <?php foreach($_subcategories as $_subcategory): ?> <li> <a href="<?php echo $_helper->getCategoryUrl($_subcategory) ?>"> <?php echo $_subcategory->getName() ?> </a> </li> <?php endforeach; ?> </ul> <?php endif; ?> <?php endif; ?> </li> <?php endforeach; ?> </ul> <?php endif; ?>