Magento Layered navigation at home page

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1.Update XML layout via CMS > Manage Pages > Homepage > Layout Update XML box:
<reference name="left">
    <block type="catalog/layer_view" name="catalog.leftnav" after="currency" template="catalog/layer/view.phtml"/>
</reference>

2.Modify a core method getCurrentCategory() in core/Mage/Catalog/Model/Layer.php
public function getCurrentCategory()
    {
        $category = $this->getData('current_category');

        if (is_null($category)) {
            if ($category = Mage::registry('current_category')) {
                $this->setData('current_category', $category);
            }
            else {
                $category = Mage::getModel('catalog/category')->load($this->getCurrentStore()->getRootCategoryId());
                $this->setData('current_category', $category);
            }
        }

        if($category != Mage::registry('current_category')) {          
            $home_category = Mage::getModel('catalog/category')->load(3);
            $this->setData('current_category', $home_category);
            $category = $this->getData('current_category');
            //return $category;
        }
     
        return $category;
    }