Hi,

[Magento version 1.7]
Today we’re gonna create a simple module to allow the addition of a link to a specific cms page to your website navigational menu, maybe an About Page or Contact Us. We can simply do that by editing the top navigation file located at /app/design/frontend/abc/theme/template/catalog/navigation/top.phtml but this would leave a .last class attribute to the last category and this might miss the design a bit. So what we will be doing is overriding renderCategoriesMenuHtml function which is responsible for drawing the menu items.

Module Installation File:
/app/etc/modules/ABC_Catalog.xml

<?xml version="1.0"?>
<config>
	<modules>
		<ABC_Catalog>
			<active>true</active>
			<codePool>local</codePool>
	 	</ABC_Catalog>
	</modules>
</config>

Moving on to the module configuration:
Module Configuration File:
/app/code/local/ABC/Catalog/etc/config.xml

<?xml version="1.0"?>

<config>
	<modules>
		<ABC_Catalog>
			<version>1.0</version>
		</ABC_Catalog>
	</modules>
	<global>
		<blocks>
			<catalog>
				<rewrite>
					<navigation>ABC_Catalog_Block_Navigation</navigation>
				</rewrite>
			</catalog>
		</blocks>
	</global>
</config>

Now to some actual code, we are overriding the render category item with a slightly modified version that takes an extra parameter that specifies whether to append the last class attribue or not to the last drawn category.
Navigation Class:
/app/code/local/ABC/Catalog/Block/Navigation.php

<?php

/**
 * Catalog navigation
 *
 * @category   Mage
 * @package    Mage_Catalog
 * @author      Yehia Abdel Salam <yehiasalam@cairocubicles.com>
 */
class ABC_Catalog_Block_Navigation extends  Mage_Catalog_Block_Navigation
{

    /**
     * Render categories menu in HTML
     *
     * @param int Level number for list item class to start from
     * @param string Extra class of outermost list items
     * @param string If specified wraps children list in div with this class
     * @return string
     */
    public function renderCategoriesMenuHtml($level = 0, $outermostItemClass = '', $childrenWrapClass = '', $markLast = true)
    {
        $activeCategories = array();
        foreach ($this->getStoreCategories() as $child) {
            if ($child->getIsActive()) {
                $activeCategories[] = $child;
            }
        }
        $activeCategoriesCount = count($activeCategories);
        $hasActiveCategoriesCount = ($activeCategoriesCount > 0);

        if (!$hasActiveCategoriesCount) {
            return '';
        }



        $html = '';
        $j = 0;

        foreach ($activeCategories as $category) {
            $html .= $this->_renderCategoryMenuItemHtml(
                $category,
                $level,
                ( $markLast ? ($j == $activeCategoriesCount - 1) : false ) ,
                ($j == 0),
                true,
                $outermostItemClass,
                $childrenWrapClass,
                true
            );
            $j++;
        }

        return $html;
    }

}

Now we could open /app/design/frontend/abc/theme/template/catalog/navigation/top.phtml and add something like this, note that we set the last parameter of renderCategoriesMenuHtml to false so it wont append any last classes

<?php $_menu = $this->renderCategoriesMenuHtml(0,'level-top', '', false) ?>
<?php if($_menu): ?>
<div class="nav-container">
    <ul id="nav">
        <?php echo $_menu ?>
        <li class="level0 nav-6 level-top last parent">
			<a href="<?php echo $this->getUrl('about-us')?>" class="level-top">
				<span>Programs &amp; Services</span>
			</a>
        </li>
    </ul>
</div>
<?php endif ?>

And thats how you create an entire module to do trivial stuff in magento.