<?php
$this_post_cat_arr = array("16", "9");

$recent = new WP_Query(array(
   "post__not_in" => array(get_the_ID()),
   "showposts" => 3,
   "category__in" => $this_post_cat_arr
));

while ($recent->have_posts()) : $recent->the_post(); ?>
   <a href="<?php the_permalink() ?>"><?php the_title(); ?></a>
<?php endwhile; ?>