Get navigation menu categories and category path url key

 <ul>  
               <?php  
                 $obj = new Mage_Catalog_Block_Navigation();  
                 $storeCategories = $obj->getStoreCategories();  
                 foreach ($storeCategories as $_category):  
               ?>  
                   <li><a href="<?php echo $this->getUrl(). $_category->getUrl_key(); ?>"><?php echo $_category->getName(); ?></a></li>  
                 <?php endforeach ?>  
             </ul>