Using Pages to create page elements

Hello All,
I have an idea for my portfolio, but am not sure I can find a way to use wordpress to make it happen, any help is greatly appreciated.

I am using pages with feature images to link to populate my portfolio. The code looks like this:

<?php
    global $post;
    $myposts = get_posts('numberposts=100&offset=news&category_name=portfolio');
    foreach($myposts as $post) :
    setup_postdata($post);
?>
<div class="workitem">
     <div class="workitem_photo"<?php the_post_thumbnail('150,200'); ?></div>
     <div class="workitem_title"><?php the_title();?></div>
     <div class="workitem_description"><?php the_excerpt(); ?></div>
     <a class="workitem_projectdetails" href="<?php the_permalink(); ?>" style="display:none;">Project Details</a>
  </div>
<?php endforeach; ?>

This works great, I can just make a page, and it updates my porfolio on the homepage. The only problem is that my portfolio has a navigation system that hinges on each of these items having overlapping class tags to catagorize each item for sorting.

Normally I would would just add the class here:
<div class="workitem ***CATEGORY***">

but this wont work if I am using pages to dynamically create it.
Is there any way I can create a custom handle in the wordpress page creation tool and then use a php reference to grag it… something like this:

<div class="workitem <?php custom_category();?><">

Here is a link to my site set up without the wordpress dynamic items implimented so you can get a feel for how the menu works.