Say I have top-level (parentless) pages called Fruit, Animals, Cars. When, say, Fruit is selected I would like to show links to the individual fruit pages below. I would like to be able to dislpay these fruits (or animals, or cars) in several groups with a space between each group of fruits.. a bit like this

    *Fruit    Animals    Cars
        
    Apple
    Kiwi
    Watermelon
    
    Banana
    Lemon
    
    Strawberry
    Raspberry

You can see in this case, I have roughy divided the fruit by color, putting a space inbetween. For cars or animals it might be another criteria. This criteria does not have to be explicitly named anywhere. So I wondering how to output this list, in a way which requires little techinical ability for the person who enters the pages in the backend.

At the moment I do this to output the child pages:

    if($post->post_parent)
    $children = wp_list_pages('depth=1&title_li=&child_of='.$post->post_parent.'&echo=0'); else
    $children = wp_list_pages('depth=1&title_li=&child_of='.$post->ID.'&echo=0');
    php echo $children; ?>

But I can't see a way to limit the output to categories, or something similar, using wp_list_pages. The nearest I can see is the 'authors' option, but it doesn't make much sense to login as different users to create different blocks in the menus...