i got it working on a post using this:
$query =’showposts=10&tag=’.$_GET[‘tag’];
if(isset($_GET[‘paged’])) $query.= ‘&paged=’.$_GET[‘paged’];
query_posts($query);
if (have_posts()) : while (have_posts()) : the_post();
hope this helps
you may want to try out this plugin called Limit Categories. this allows you to limit the categories a user can post to.
http://redalt.com/Resources/Plugins/Limit+Categories
