$product = Mage::getModel(’catalog/product’);
$attributes = Mage::getResourceModel(’eav/entity_attribute_collection’)
→setEntityTypeFilter($product→getResource()→getTypeId())
→addFieldToFilter(’attribute_code’, ‘manufacturer’) // This can be changed to any attribute code
→load(false);
$attribute = $attributes→getFirstItem()→setEntity($product→getResource());
/* @var $attribute Mage_Eav_Model_Entity_Attribute */
$manufacturers = $attribute→getSource()→getAllOptions(false);