I’m somewhat in the same situation myself – I would like to take a query and offset the results by 5 so that I get the *next* twenty posts in the list. This is the query I have written out right now, but it isn’t working:
<div id="content">
<div id="primary">
<?php $my_query = new WP_Query('category_name=content&showposts=20&offset=5');
while ($my_query->have_posts()) : $my_query->the_post();
if( $post->ID == $do_not_duplicate ) continue; update_post_caches($posts);
?>
<div class="postNormal" id="post-<?php the_ID(); ?>">
<h1><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_title(); ?></a></h1>
<div class="entry">
<p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_excerpt('Read the rest of this entry »'); ?></a></p>
</div>
</div>
<?php endwhile; ?>