This question is bit specific for Joomla.
I have a main menu consisting of:
Home|About US|Privacy Policy|Portfolio|Contacts US.
Each menu it
The easiest way to accomplish this in 2.5+ is:
$app = JFactory::getApplication();
$menu = $app->getMenu();
$menu_items = $menu->getItems('menutype', 'mainmenu');
Just replace 'mainmenu' with the menutype that you want to pull. This would equate to the system name for your menu, the same as you would select in the menu module.
Edit in response to @betweenbrain's question below: Get the menu object the same way as above, then:
// To get menu items filtered by access level of current user.
$filtered_menu_items = $menu->getItems(null, null);
// To get all menu items, unfiltered.
$all_menu_items = $menu->getMenu();