Recursive function for Magento that provides useful information regarding a specified category and all children.

getChildCategories.php

<?php
	function getCategories(Mage_Catalog_Model_Category $ParentCategory) {
		$return = array();
		foreach(explode(',', $ParentCategory->getChildren()) as $categoryId) {
			$Category = Mage::getModel('catalog/category')->load($categoryId);
			$return[$categoryId] = array(
				'id'       => $Category->getId(),
				'name'     => $Category->getName(),
				'slug'     => $Category->getUrlKey(),
				'url'      => $Category->getUrl(),
				'active'   => $Category->getIsActive(),
				'children' => array()
			);
			if($Category->getChildren()) {
				$return[$categoryId]['children'] = getCategories($Category, $return);
			}
		}
		return $return;
	}