A recent client needed to bring the tiered pricing seen on the product page into their category list views. While there is a few approaches in this, the easiest method I found was to add this snippet to the desired location in
/default/template/catalog/product/list.phtml
<?php $this->setProduct(Mage::getModel('catalog/product')->setStoreId(Mage::app()->getStore()->getId())->load($_product->getId()))
?>
<?php echo $this->getTierPriceHtml() ?>