Exclude Categories from the_excerpt

Hi,
I have a static page as my homepage where I display an excerpt from the most recent posts, as opposed to the traditional WordPress index page. What I’m trying to do is exclude posts of a couple different categories from appearing here. My code looks like this:

<?php $posts = get_posts( "numberposts=1" ); ?>
<?php if( $posts ) : ?>
     <?php foreach( $posts as $post ) : setup_postdata( $post ); ?>
       <div class="entry">
          <?php the_excerpt(); ?>
		  <a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link: <?php the_title(); ?>">Read more...</a>
       </div>
     </div>
   <?php endforeach; ?>
<?php endif; ?>

Any help would be most appreciated, as I’m a PHP noob and there’s probably an obvious solution I overlooked.