split wordpress loop into columns of categories and associated posts

What you will need to do is loop through an array of category IDs. For example:

$categories = get_categories();

Then loop through the categories, and use the category id in your query_posts:

foreach($categories as $category) {
    $args = array(
    'cat' = $category->ID
    )
    // return your loop here...
}

Or something… assuming I understand your question.