You can add category filter in manage products page to sort your product, you can do it manually just add one column category on product grid.
Here is a nice answer of adding category column in product grid https://stackoverflow.com/questions/3472702/add-categories-column-to-the-product-grid-in-magento-admin
Just put below code in your Grid.php file
$collection = Mage::getModel('catalog/category')->getCollection()->addAttributeToSelect('name');
$options = array();
foreach ($collection as $item){
if($item->getId() != ''){
$options[$item->getId()] = $item->getName();
}
}
$this->addColumn('category_ids',
array(
'header' => Mage::helper('catalog')->__('Categories'),
'index' => 'single_category_id',
'width' => '150px',
'type' => 'options',
'options' => $options
));
Or else you can use free extension which are available to add extra grid in your manage product grid.
This will add extra category column in grid and you are able to sort your product according to category.
http://www.magentocommerce.com/magento-connect/enhanced-admin-product-grid.html
http://www.magentocommerce.com/magento-connect/enhanced-admin-grids-editor.html