ToHtml

<?php
//Get current category url
$current_category = Mage::registry('current_category')->getUrl();

//Get brandname
$brandname = Mage::getModel('catalog/product')->load($_product->getId())->getAttributeText('manufacturer');

//Strip .html and add the stuff from the layered navigation to it
$brandurl = str_replace(".html", "/l/". strtolower($brandname) .".html", $current_category);
$brandnamemurl = "of <a href="" . $brandurl . "">" . $brandname . "</a>";

//breadcrumb stuff
$breadcrumbs = $this->getLayout()->getBlock('breadcrumbs');
$breadcrumbs->addCrumb('manufacturer', array('label'=>$brandnamemurl, 'title'=>$brandname));

echo $this->getLayout()->getBlock('breadcrumbs')->toHtml();
?>