Free

Free:

List of free extensions http://www.9magentothemes.com

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HERE IS THE SOLUTION: 
delete the following file from your root folder /magento/ installation

(or)

maintenance.flag

e.g. rm ./magento/maintenance.flag

to call contact form in CMS page.

Go to CMS> Manage Pages interface

Insert the below code in content area

{{block type="core/template" name="contactForm" form_action="/contacts/index/post" template="contacts/form.phtml"}}

To print product category name in product description page

Go to catalog/product/view.phtml

<?php $categories = $_product->getCategoryIds(); ?>
<?php foreach($categories as $i => $_category_id): ?>
<?php $_category = Mage::getModel('catalog/category')->load($_category_id) ?>
<a href="<?php echo $_category->getUrl() ?>"><?php echo $_category->getName() ?></a>
<?php endforeach; ?>

To add Sitemap to a Magento websites

It helps mostly for Search Engine Optimization(SEO).

-> Goto System> Configuration> Catalog> Google Sitemap. Enable all the options in there

-> Goto System> Configuration> Catalog> Catalog> Sitemap and enable the Sitemap Creation option.