how to separate categories in loop.php?

Here is something i have used recently… not too complicated…
First.. we call all categories.
Then.. we get posts inside each category using foreach

<?php  
 $allcats = get_categories('child_of=".get_query_var("cat')); 

    foreach ($allcats as $cat) :
    $args = array(
    'posts_per_page' => 3, // max number of post per category

    'category__in' => array($cat->term_id)
    );

    $customInCatQuery = new WP_Query($args); 

    if ($customInCatQuery->have_posts()) : 
    echo '<div>';
    echo '<h3>'.$cat->name.'</h3>';
    echo '<ul>';    
    while ($customInCatQuery->have_posts()) : $customInCatQuery->the_post(); ?>

    <li><a href="https://wordpress.stackexchange.com/questions/66508/<?php the_permalink(); ?>"><?php the_title(); ?></a></li>

<?php
endwhile; 
echo '</ul></div>'; 
?>

<?php else : 
echo 'No post published in:'.$cat->name;                
endif; 
wp_reset_query();
endforeach; 
?>

Hope this helps…
Have a gr8 day, Sagive.