Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 6065)
+++ wp-includes/post.php	(working copy)
@@ -178,20 +178,21 @@
 	else
 		parse_str($args, $r);
 
-	$defaults = array('numberposts' => 5, 'offset' => 0, 'category' => 0,
+	$defaults = array('numberposts' => 5, 'offset' => 0, 'category' => '', 'category_exclude' = 0,
 		'orderby' => 'post_date', 'order' => 'DESC', 'include' => '', 'exclude' => '',
 		'meta_key' => '', 'meta_value' =>'', 'post_type' => 'post', 'post_status' => 'publish', 'post_parent' => 0);
 	$r = array_merge($defaults, $r);
 	extract($r, EXTR_SKIP);
 	$numberposts = (int) $numberposts;
 	$offset = (int) $offset;
-	$category = (int) $category;
+	// $category = (int) $category; should remain textual
+	$category_exclude = ( 1 == (int)$category_exclude ? 'NOT' : '');
 	$post_parent = (int) $post_parent;
 
 	$inclusions = '';
 	if ( !empty($include) ) {
 		$offset = 0;    //ignore offset, category, exclude, meta_key, and meta_value, post_parent if using include
-		$category = 0;
+		$category = '';
 		$exclude = '';
 		$meta_key = '';
 		$meta_value = '';
@@ -232,7 +233,7 @@
 	$query .= empty( $post_type ) ? '' : "AND post_type = '$post_type' ";
 	$query .= empty( $post_status ) ? '' : "AND post_status = '$post_status' ";
 	$query .= "$exclusions $inclusions " ;
-	$query .= empty( $category ) ? '' : "AND ($wpdb->posts.ID = $wpdb->post2cat.post_id AND $wpdb->post2cat.category_id = " . $category. ") ";
+	$query .= empty( $category ) ? '' : "AND ($wpdb->posts.ID = $wpdb->post2cat.post_id AND $wpdb->post2cat.category_id $category_exclude IN (" . $category. ")) ";
 	$query .= empty( $post_parent ) ? '' : "AND $wpdb->posts.post_parent = '$post_parent' ";
 	$query .= empty( $meta_key ) | empty($meta_value)  ? '' : " AND ($wpdb->posts.ID = $wpdb->postmeta.post_id AND $wpdb->postmeta.meta_key = '$meta_key' AND $wpdb->postmeta.meta_value = '$meta_value' )";
 	$query .= " GROUP BY $wpdb->posts.ID ORDER BY " . $orderby . ' ' . $order;