Using my this post you can add Product Configurable option which are in stock like size, color etc. on your Product listing page.

You can add some simple code to our website, that will show which options are available, so when your customer is looking at your list pages, where you have multiple products being shown, you can clearly show them which sizes or colors are still in stock.

As you can see in the image above, the available shoe sizes are being shown on each product. So your customer can easily find out the product for what they are looking.

To do this, use following code in  app/design/frontend/default/my-theme/template/catalog/product/

<?php
$sizes = array();
if($_product->isConfigurable()){
    $allProducts = $_product->getTypeInstance(true)->getUsedProducts(null, $_product);
    foreach ($allProducts as $subproduct) {
        if ($subproduct->isSaleable() && floor($subproduct->getStockItem()->getQty()) > 0 ) {
            $sizes[] = $subproduct->getAttributeText('config_sizes');
        }
    }
    if(count($sizes)>0) {
        sort($sizes);
        ?>
        <div>
        Sizes: <? echo implode(", ", $sizes); ?>
        </div>
        <?
    }
}
?>

Replace 'config_sizes' with your attribute code.