Hello Friends, If you want to display the Out of Stock product at the end of the product list Then go to following manner:

1. First go to app/code/core/Mage/catelog/Block/product/list.php

2. then find the function _getProductCollection().

3. then find the following line

<?php
$this->_productCollection = $layer->getProductCollection();
?>

modified this line, this following way

<?php
$this->_productCollection = $layer->getProductCollection()->joinField('inventory_in_stock', 'cataloginventory_stock_item', 'is_in_stock', 'product_id=entity_id','is_in_stock>=0', 'left')->setOrder('inventory_in_stock','desc');
?>

4. See your product listing page.

Thanks,