Index: header.php
===================================================================
--- header.php	(revision 4501)
+++ header.php	(working copy)
@@ -18,6 +18,10 @@
 );
 
 $GLOBALS['pagetitle'] = __( 'Plugin Directory — Free WordPress Plugins', 'wporg-plugins' );
+if ( is_singular( 'plugin' ) ) {
+    /* Translators: The name of the plugin. */
+    $GLOBALS['pagetitle'] = sprintf( __( '%s — WordPress Plugin Directory', 'wporg-plugins' ), get_the_title( get_the_ID() ) );
+}
 require WPORGPATH . 'header.php';
 ?>
 <div id="page" class="site">