Show out of stock at end From http://stackoverflow.com/questions/15879978/magento-out-of-stock-products-showing-last-in-the-category-page

Show out of stock at end

Create an observer and add event listener to catalog_product_collection_load_before

/**
 * Fires before a product collection is loaded
 *
 * @param Varien_Event_Observer $observer
 */
public function catalog_product_collection_load_before($observer)
{
    $collection = $observer->getCollection();
    $collection->getSelect()->joinLeft(
        array('_inventory_table'=>$collection->getTable('cataloginventory/stock_item')),
        "_inventory_table.product_id = e.entity_id",
        array('is_in_stock', 'manage_stock')
    );
    $collection->addExpressionAttributeToSelect(
        'on_top',
        '(CASE WHEN (((_inventory_table.use_config_manage_stock = 1) AND (_inventory_table.is_in_stock = 1)) OR  ((_inventory_table.use_config_manage_stock = 0) AND (1 - _inventory_table.manage_stock + _inventory_table.is_in_stock >= 1))) THEN 1 ELSE 0 END)',
        array()
    );
    $collection->getSelect()->order('on_top DESC');
    // Make sure on_top is the first order directive
    $order = $collection->getSelect()->getPart('order');
    array_unshift($order, array_pop($order));
    $collection->getSelect()->setPart('order', $order);
}