Index: includes/Category.php
===================================================================
--- includes/Category.php	(revision 92077)
+++ includes/Category.php	(working copy)
@@ -306,4 +306,73 @@
 
 		return $ret;
 	}
+
+	/**
+	 * Delete this category from the database if it has no members and no
+	 * description page.
+	 *
+	 * @return bool True on successful delete, false on failed delete or 
+	 * no action taken
+	 */
+	public function deleteIfUnused() {
+		$title = $this->getTitle();
+		
+		// Does the category description page exist? If so, skip.
+		if ( !is_null( $title )
+			&& $title->exists() )
+		{
+			return false;
+		}
+		
+		// Are there any members of the category? If so, skip.
+		if (   $this->getPageCount() != 0
+			|| $this->getSubcatCount() != 0
+			|| $this->getFileCount() != 0 )
+		{
+			return false;
+		}
+		
+		// Make sure the counts are correct, just in case we end up in a race condition
+		// Overhead shouldn't be significant because:
+		// 1) Not many categories will need to be rechecked to begin with
+		// 2) Those that are will either be empty or small
+		$this->refreshCounts();
+		if (   $this->getPageCount() != 0
+			|| $this->getSubcatCount() != 0
+			|| $this->getFileCount() != 0 )
+		{
+			return false;
+		}
+		
+		return $this->deleteFromTable();
+	}
+
+	
+	/**
+	 * Delete this category from the database (by cat_id)
+	 *
+	 * @return bool True on success, false on failure
+	 */
+	public function deleteFromTable() {
+		if ( wfReadOnly() ) {
+			return false;
+		}
+
+		// It would be great if we knew what category we were deleting
+		if ( $this->mID === null ) {
+			// Make sure it's still there
+			if ( !$this->initialize() ) {
+				return false;
+			}
+		}
+
+		$dbw = wfGetDB( DB_MASTER );
+		$dbw->begin();
+
+		// Delete.
+		$ret = $dbw->delete( 'category', array( 'cat_id' => $this->mID ), __METHOD__ );
+		$dbw->commit();
+
+		return $ret;
+	}
 }
Index: maintenance/cleanupCategories.php
===================================================================
--- maintenance/cleanupCategories.php	(revision 0)
+++ maintenance/cleanupCategories.php	(revision 0)
@@ -0,0 +1,101 @@
+<?php
+/**
+ * Script to clean up categories with no members.
+ *
+ * Usage: php cleanupCategories.php [--fix]
+ * Options:
+ *   --fix  Actually clean up categories; otherwise just checks for them
+ *
+ * Copyright (c) 2011 Dan Collins <dcollinsn at gmail.com>
+ * http://www.mediawiki.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Dan Collins <dcollinsn at gmail.com>
+ * @ingroup Maintenance
+ */
+
+require_once( dirname( __FILE__ ) . '/cleanupTable.inc' );
+
+class CategoryCleanup extends TableCleanup {
+	protected $defaultParams = array(
+		'table' => 'category',
+		'conds' => array(),
+		'index' => 'cat_id',
+		'callback' => 'processRow',
+	);
+	
+	public function __construct() {
+		parent::__construct();
+		$this->mDescription = "Script to clean up categories with no members";
+	}
+
+	protected function processRow( $row ) {
+		global $wgContLang;
+		
+		// Create the necessary objects
+		$category = Category::newFromName( $row->cat_title );
+		$title = $category->getTitle();
+
+		// Does the category description page exist? If so, skip.
+		if ( !is_null( $title )
+			&& $title->exists() )
+		{
+			$this->output( "DEBUG: $row->cat_title has a description page\n" );
+			return $this->progress( 0 );  // all is fine
+		}
+
+		// Are there any members of the category? If so, skip.
+		if (   $row->cat_pages != 0
+			|| $row->cat_subcats != 0
+			|| $row->cat_files != 0 ) 
+		{
+			$this->output( "DEBUG: $row->cat_title has members:\n" );
+			$this->output( "DEBUG:  $row->cat_pages pages, $row->cat_subcats subcats, $row->cat_files files\n" );
+			return $this->progress( 0 );  // all is fine
+		}
+		
+		// Make sure the counts are correct, just in case we end up in a race condition
+		// Overhead shouldn't be significant because:
+		// 1) Not many categories will need to be rechecked to begin with
+		// 2) Those that are will either be empty or small
+		$category->refreshCounts();
+		if (   $category->getPageCount() != 0
+			|| $category->getSubcatCount() != 0
+			|| $category->getFileCount() != 0 )
+		{
+			$this->output( "DEBUG: $row->cat_title has members after refresh\n" );
+			return $this->progress( 0 );
+		}
+
+		$this->output( "category $row->cat_title has no members or description page\n" );
+		$this->removeCategory( $row, $category );
+		return $this->progress( 1 );
+	}
+
+	protected function removeCategory( $row, $category ) {
+		if ( $this->dryrun ) {
+			$this->output( "DRY RUN: would remove $row->cat_id ($row->cat_title)\n" );
+		} else {
+			$this->output( "Removing $row->cat_id ($row->cat_title)\n" );
+			$category->deleteFromTable();
+		}
+	}
+}
+
+$maintClass = "CategoryCleanup";
+require_once( RUN_MAINTENANCE_IF_MAIN );