Create new custom category attribute - Magento

if you want to create custom textbox attribute use this code.

Step 1 

   equire_once('app/Mage.php');

Mage::app()->setCurrentStore(Mage::getModel('core/store')->load(Mage_Core_Model_App::ADMIN_STORE_ID));
$installer = new Mage_Sales_Model_Mysql4_Setup;
$attribute  = array(
    'group'         => 'General',
    'input'         => 'text',
    'type'          => 'varchar',
    'label'         => 'Brand value',
    'backend'       => '',
    'visible'       => true,
    'required'      => false,
    'visible_on_front' => true,
    'global'        => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
);
$installer->addAttribute('catalog_category', 'brand_value', $attribute);
$installer->endSetup();

Step 2 paste this code in header.phml file and check category menu.

if you want to create custom selectbox for Yes/no attribute use this code 
require_once('app/Mage.php');
Mage::app()->setCurrentStore(Mage::getModel('core/store')->load(Mage_Core_Model_App::ADMIN_STORE_ID));
$installer = new Mage_Sales_Model_Mysql4_Setup;
$attribute  = array(
    'group'                     => 'General',
        'input'                     => 'select',
        'type'                      => 'int',
        'label'                     => 'Is Mega Menu',
        'source'                    => 'eav/entity_attribute_source_boolean',
        'global'                    => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
        'visible'                   => 1,
        'required'                  => 0,
        'visible_on_front'          => 0,
        'is_html_allowed_on_front'  => 0,
        'is_configurable'           => 0,
        'searchable'                => 0,
        'filterable'                => 0,
        'comparable'                => 0,
        'unique'                    => false,
        'user_defined'              => false,
        'default'           => '0',
        'is_user_defined'           => false,
        'used_in_product_listing'   => true
);
$installer->addAttribute('catalog_category', 'mega_menu', $attribute);
$installer->endSetup();