$coll = Mage::getModel('sales/order')->getCollection();

$fn = Mage::getModel('eav/entity_attribute')->loadByCode('1', 'firstname');

$ln = Mage::getModel('eav/entity_attribute')->loadByCode('1', 'lastname');

$coll->getSelect()

    ->join(array('ce1' => 'customer_entity_varchar'), 'ce1.entity_id=main_table.customer_id', array('firstname' => 'value'))

    ->where('ce1.attribute_id='.$fn->getAttributeId()) 

    ->join(array('ce2' => 'customer_entity_varchar'), 'ce2.entity_id=main_table.customer_id', array('lastname' => 'value'))

    ->where('ce2.attribute_id='.$ln->getAttributeId()) 

    ->columns(new Zend_Db_Expr("CONCAT(`ce1`.`value`, ' ',`ce2`.`value`) AS fullname"));

print_r($coll->getData());

require "app/Mage.php";

umask(0);

Mage::app();

$collection = Mage::getModel('log/visitor_online')->prepare()->getCollection();

//Get all the customers that are logged in......

foreach($collection->getData() as $cust) {

        echo 'Customer ID: '.$cust['customer_id'] . '<br/>';

        echo 'Last URL visited: '.$cust['last_url'] . '<br/>';

        echo 'First visit: '.$cust['first_visit_at'] . '<br/>';

        echo 'Last visit: '.$cust['last_visit_at'] . '<br/>';

        echo '======================<br/>';

}

//Get any particular customer, if he's currently logged in or not.....

$collection->addFieldToFilter('customer_id', 5)->addCustomerData(); //5 is customer ID of customer you want to check

if($collection->count()) {

    echo 'Customer is logged in';

} else {

    echo 'Customer is NOT logged in';

}

<?php

class Mage_Catalog_Block_Product_Special extends Mage_Catalog_Block_Product_List

{

    protected function _getProductCollection()

    {

        if (is_null($this->_productCollection)) {

            $categoryID = $this->getCategoryId();

            if($categoryID)

            {

              $category = new Mage_Catalog_Model_Category();

              $category->load($categoryID); // this is category id

              $collection = $category->getProductCollection();

            } else

            {

              $collection = Mage::getResourceModel('catalog/product_collection');

            }

            $todayDate = date('m/d/y');

            $tomorrow = mktime(0, 0, 0, date('m'), date('d')+1, date('y'));

            $tomorrowDate = date('m/d/y', $tomorrow);

            Mage::getModel('catalog/layer')->prepareProductCollection($collection);

            $collection->addAttributeToSort('created_at', 'desc');

            $collection->addStoreFilter();

            $collection->addAttributeToFilter('special_from_date', array('date' => true, 'to' => $todayDate))

                ->addAttributeToFilter('special_to_date', array('or'=> array(

                0 => array('date' => true, 'from' => $tomorrowDate),

                1 => array('is' => new Zend_Db_Expr('null')))

                ), 'left');

            $numProducts = $this->getNumProducts() ? $this->getNumProducts() : 0;

            $collection->setPage(1, $numProducts)->load();

            $this->_productCollection = $collection;

        }

        return $this->_productCollection;

    }

}