function getSelectBox($attributeCode, $label = '', $defaultSelect = null, $extraParams = null){
    $options            = array();
    $product            = Mage::getModel('catalog/product');
    $attribute          = $product->getResource()->getAttribute($attributeCode);
    if($attribute->usesSource()){
        $options = $attribute->getSource()->getAllOptions(false);
        array_unshift($options, array('label' => $label, 'value' => ''));
    }

    $select = Mage::app()->getLayout()->createBlock('core/html_select')
            ->setName($attributeCode)
            ->setId($attributeCode)
            ->setTitle($label)
            ->setValue($defaultSelect)
            ->setExtraParams($extraParams)
            ->setOptions($options);
    return $select->getHtml();
}

<?php echo Mage::helper('function')->getSelectBox('manufacturer', 'Select Manufacturer'); ?>

<li>
 <a href="#">Browse by Manufacturer</a>
 <ul>
<?php $attribute = Mage::getSingleton('eav/config')->getAttribute('catalog_product', 'manufacturer');
if ($attribute->usesSource()) {
$options = $attribute->getSource()->getAllOptions(false);
foreach ($options as $option)
{
    echo '<li style="list-style:none"><a href="'.Mage::getUrl('catalogsearch/advanced/result').'?manufacturer%5B%5D='.$option['value'].'">'.$option['label'].'</a></li>';
}
} ?>
 </ul>
</li>