You may use following code
$collection=Mage::getResourceModel('catalog/product_collection') ->addAttributeToSelect('name') ->addAttributeToSelect('sku') ->addAttributeToSelect('special_price') ->addAttributeToSelect('price'); $collection->addAttributeToFilter('special_from_date',array(array('from' => Mage::getModel('core/date')->gmtDate()), array('special_from_date', 'null'=>true))); $collection->addAttributeToFilter('special_to_date',array(array('to' => Mage::getModel('core/date')->gmtDate()), array('special_to_date', 'null'=>true)));
$collection=Mage::getResourceModel('catalog/product_collection')
->addAttributeToSelect('name')
->addAttributeToSelect('sku')
->addAttributeToSelect('special_price')
->addAttributeToSelect('price');
$collection->addAttributeToFilter('special_from_date',array(array('from' => Mage::getModel('core/date')->gmtDate()),
array('special_from_date', 'null'=>true)));
$collection->addAttributeToFilter('special_to_date',array(array('to' => Mage::getModel('core/date')->gmtDate()),
array('special_to_date', 'null'=>true)));