Featured post – Calling thumbnails

Hi,

I am currently creating a portfolio site using WordPress as the CMS I have created a query for my featured post so I can display a few thumbnails:

$featured = new WP_Query('category_name=featured&showposts=6');

while ($featured->have_posts()):
$featured->the_post();

I then need to call the thumbnails but I have been having trouble with the next bit of php:

for ($p=; $p<=24; $i++) {
$featured = get_post_meta($p, 'thumbnail_1', true);
$link = bloginfo('url')."?p=".$p;
}
echo "<a href='".$link."'><img src='".$featured."' class='thumbnail' alt='thumbnail'/></a>";

Help!

Thanks,
Sam