Display out-of-stock products part of a Configurable Product

In a situation where you want Magento to display out of stock product options of a configurable products, overriding getAllowProducts() function in Mage_Catalog_Block_Product_View_Type_Configurable is where you should be looking, change

if ($product->isSaleable()) 
{
         $products[] = $product;
}

to

$products[] = $product;

Bingo!!!