How To call Shop By brand in magento

 first you make one phtml file path is app/design/frontend/base/default/template/catalog/navigation/vert_brand.phtml

put below code in this phtml file

<div class="leftbrand_menu">
             <?php
$product = Mage::getModel('catalog/product');
$attributes = Mage::getResourceModel('eav/entity_attribute_collection')->setEntityTypeFilter($product->getResource()->getTypeId())->addFieldToFilter('attribute_code', 'manufacturer');
$attribute = $attributes->getFirstItem()->setEntity($product->getResource());
$manufacturers = $attribute->getSource()->getAllOptions(false);
?>
<ul id="manufacturer_list"><?php foreach ($manufacturers as $manufacturer): ?>
<li><a href="<?php echo $this->getUrl('shop-by-brand')."?manufacturer=".$manufacturer['value'] ?>"><?php echo $manufacturer['label'] ?></a>
</li>
<?php endforeach; ?>   </ul>
            </div>

call this page in left side so open  catalog.xml file inleft part put below xml

<block type="catalog/navigation" name="catalog.vertnav" template="catalog/navigation/vert_brand.phtml" />

and after  make a cms page like brand

in this page in content part put below code

{{block type="catalog/product_list" template="catalog/product/shop_by_brand.phtml"}}

put identifier(url key) is shop-by-brand in the page.and last one make a another phtml page path is
         app/design/frontend/base/default/template/catalog/product/shop_by_brand.phtml

put below code

<?php
    $_productCollection=$this->getLoadedProductCollection();
    $_helper = $this->helper('catalog/output');
?>
<?php
    $bid = $_GET['manufacturer']; // the brand / manufacturer ID
    $products = Mage::getModel('catalog/product')->getCollection();
    $products->addAttributeToFilter('manufacturer', array('in' => array($bid)));
    $products->addAttributeToSelect('*');
    $products->load();   
    ?>





<div class="page-title category-title">
<h1><?php echo $this->__('Shop By') ?>
<?php $aaa = $_REQUEST['manufacturer']; ?>

<?php
$product = Mage::getModel('catalog/product');
$attributes = Mage::getResourceModel('eav/entity_attribute_collection')->setEntityTypeFilter($product->getResource()->getTypeId())->addFieldToFilter('attribute_code', 'manufacturer');
$attribute = $attributes->getFirstItem()->setEntity($product->getResource());
$manufacturers = $attribute->getSource()->getAllOptions(false);
foreach ($manufacturers as $manufacturer): ?>
<?php $bbb = $manufacturer['value'];

if($aaa  ==  $bbb)
{
echo $manufacturer['label'];
}
 ?>

<?php endforeach; ?> <?php echo $this->__('Brand') ?></h1>
</div>


<?php if(!$products->count()): ?>
<p class="note-msg">
<?php echo $this->__('There are no products matching the selection.') ?></p>
<?php else: ?>
<div class="category-products">


    <?php echo $this->getToolbarHtml() ?>
    <?php // List mode ?>
    <?php if($this->getMode()!='grid'): ?>
    <?php $_iterator = 0; ?>
    <ol class="products-list" id="products-list">
    <?php foreach ($products as $_product): ?>
        <li class="item<?php if( ++$_iterator == sizeof($products) ): ?> last<?php endif; ?>">
            <?php // Product Image ?>
            <a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->stripTags($this->getImageLabel($_product, 'small_image'), null, true) ?>" class="product-image"><img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(135); ?>" width="135" height="135" alt="<?php echo $this->stripTags($this->getImageLabel($_product, 'small_image'), null, true) ?>" /></a>
            <?php // Product description ?>
            <div class="product-shop">
                <div class="f-fix">
                    <?php $_productNameStripped = $this->stripTags($_product->getName(), null, true); ?>
                   
                    <h5><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>"><?php echo $this->htmlEscape($_product->getName()) ?></a></h5>
                    <?php /*?><h2 class="product-name"><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $_productNameStripped; ?>"><?php echo $_helper->productAttribute($_product, $_product->getName() , 'name'); ?></a></h2><?php */?>
                    <?php if($_product->getRatingSummary()): ?>
                    <?php echo $this->getReviewsSummaryHtml($_product) ?>
                    <?php endif; ?>
                    <?php echo $this->getPriceHtml($_product, true) ?>
                    <?php if($_product->isSaleable()): ?>
                        <p><button type="button" title="<?php echo $this->__('Add to Cart') ?>" class="button btn-cart" onclick="setLocation('<?php echo $this->getAddToCartUrl($_product) ?>')"><span><span><?php echo $this->__('Add to Cart') ?></span></span></button></p>
                    <?php else: ?>
                        <p class="availability out-of-stock"><span><?php echo $this->__('Out of stock') ?></span></p>
                    <?php endif; ?>
                    <div class="desc std">
                    <?php echo nl2br($_product->getShortDescription()) ?>
                <a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>"><small><?php echo $this->__('Learn More') ?></small></a>
                        <?php /*?><?php echo $_helper->productAttribute($_product, $_product->getShortDescription(), 'short_description') ?>
                        <a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $_productNameStripped ?>" class="link-learn"><?php echo $this->__('Learn More') ?></a><?php */?>
                    </div>
                    <ul class="add-to-links">
                        <?php if ($this->helper('wishlist')->isAllow()) : ?>
                            <li><a href="<?php echo $this->helper('wishlist')->getAddUrl($_product) ?>" class="link-wishlist"><?php echo $this->__('Add to Wishlist') ?></a></li>
                        <?php endif; ?>
                        <?php if($_compareUrl=$this->getAddToCompareUrl($_product)): ?>
                            <li><span class="separator">|</span> <a href="<?php echo $_compareUrl ?>" class="link-compare"><?php echo $this->__('Add to Compare') ?></a></li>
                        <?php endif; ?>
                    </ul>
                </div>
            </div>
        </li>
    <?php endforeach; ?>
    </ol>
    <script type="text/javascript">decorateList('products-list', 'none-recursive')</script>

    <?php else: ?>

    <?php // Grid Mode ?>

    <?php $_collectionSize = $products->count() ?>
    <?php $_columnCount = $this->getColumnCount(); ?>
    <?php $i=0; foreach ($products as $_product): ?>
        <?php if ($i++%$_columnCount==0): ?>
        <ul class="products-grid">
        <?php endif ?>
            <li class="item<?php if(($i-1)%$_columnCount==0): ?> first<?php elseif($i%$_columnCount==0): ?> last<?php endif; ?>">
                <a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->stripTags($this->getImageLabel($_product, 'small_image'), null, true) ?>" class="product-image"><img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(135); ?>" width="135" height="135" alt="<?php echo $this->stripTags($this->getImageLabel($_product, 'small_image'), null, true) ?>" /></a>
                <?php /*?><h2 class="product-name"><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->stripTags($_product->getName(), null, true) ?>"><?php echo $_helper->productAttribute($_product, $_product->getName(), 'name') ?></a></h2><?php */?>
                <h5><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>"><?php echo $this->htmlEscape($_product->getName()) ?></a></h5>
                <?php if($_product->getRatingSummary()): ?>
                <?php echo $this->getReviewsSummaryHtml($_product, 'short') ?>
                <?php endif; ?>
                <?php echo $this->getPriceHtml($_product, true) ?>
                <div class="actions">
                    <?php if($_product->isSaleable()): ?>
                        <button type="button" title="<?php echo $this->__('Add to Cart') ?>" class="button btn-cart" onclick="setLocation('<?php echo $this->getAddToCartUrl($_product) ?>')"><span><span><?php echo $this->__('Add to Cart') ?></span></span></button>
                    <?php else: ?>
                        <p class="availability out-of-stock"><span><?php echo $this->__('Out of stock') ?></span></p>
                    <?php endif; ?>
                    <ul class="add-to-links">
                        <?php if ($this->helper('wishlist')->isAllow()) : ?>
                            <li><a href="<?php echo $this->helper('wishlist')->getAddUrl($_product) ?>" class="link-wishlist"><?php echo $this->__('Add to Wishlist') ?></a></li>
                        <?php endif; ?>
                        <?php /*?><?php if($_compareUrl=$this->getAddToCompareUrl($_product)): ?>
                            <li><span class="separator">|</span> <a href="<?php echo $_compareUrl ?>" class="link-compare"><?php echo $this->__('Add to Compare') ?></a></li>
                        <?php endif; ?><?php */?>
                    </ul>
                </div>
            </li>
        <?php if ($i%$_columnCount==0 || $i==$_collectionSize): ?>
        </ul>
        <?php endif ?>
        <?php endforeach ?>
        <script type="text/javascript">decorateGeneric($$('ul.products-grid'), ['odd','even','first','last'])</script>
    <?php endif; ?>

    <div class="toolbar-bottom">
        <?php echo $this->getToolbarHtml() ?>
    </div>
</div>
<?php endif; ?>