Magento get Bestseller products.

To display bestselling product we need to create a block file.

class Magento_kamal_Block_Bestsellers extends Mage_Core_Block_Template
{
    public function getBestsellerProducts()
    {
        $storeId = (int) Mage::app()->getStore()->getId();
        // Date
        $date = new Zend_Date();
        $toDate = $date->setDay(1)->getDate()->get('Y-MM-dd');
        $fromDate = $date->subMonth(1)->getDate()->get('Y-MM-dd');
        $collection = Mage::getResourceModel('catalog/product_collection')
            ->addAttributeToSelect(Mage::getSingleton('catalog/config')->getProductAttributes())
            ->addStoreFilter()
            ->addPriceData()
            ->addTaxPercents()
            ->addUrlRewrite()
            ->setPageSize(6);
        $collection->getSelect()
            ->joinLeft(
                array('aggregation' => $collection->getResource()->getTable('sales/bestsellers_aggregated_monthly')),
                "e.entity_id = aggregation.product_id AND aggregation.store_id={$storeId} AND aggregation.period BETWEEN '{$fromDate}' AND '{$toDate}'",
                array('SUM(aggregation.qty_ordered) AS sold_quantity')
            )
            ->group('e.entity_id')
            ->order(array('sold_quantity DESC', 'e.created_at'));
        Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($collection);
        Mage::getSingleton('catalog/product_visibility')->addVisibleInCatalogFilterToCollection($collection);
        return $collection;
    }
}

After that we need to create bestsellers.phtml file.

<div class="box-best-sellers"> 
<h2>Best Selling Products</h2>
<table border="0" cellspacing="0">
    <tbody>
    <?php $counter=0; foreach ($this->getBestsellerProducts() as $product): ?>
        <?php if ($counter%2 == 0): ?><tr class="<?php echo $counter%4 ? 'even' : 'odd'; ?>"><?php endif ?>
        <td>
            <a href="<?php echo $product->getProductUrl() ?>"><img class="product-img" src="<?php echo $this->helper('catalog/image')->init($product, 'small_image')->resize(99); ?>" alt="<?php echo $this->stripTags($this->getImageLabel($product, 'small_image'), null, true) ?>" width="95" border="0" /></a>
            <div class="product-description">
                <p><a href="<?php echo $product->getProductUrl() ?>"><?php echo $this->stripTags($product->getName(), null, true); ?></a></p>
            </div>
        </td>
        <?php if ($counter++%2): ?></tr><?php endif ?>
    <?php endforeach; ?>
    </tbody>
</table>
</div>

I hope it will help...