Index: modules/block/block.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.module,v
retrieving revision 1.427
diff -u -p -r1.427 block.module
--- modules/block/block.module	31 Jul 2010 12:54:58 -0000	1.427
+++ modules/block/block.module	10 Sep 2010 17:49:17 -0000
@@ -317,6 +317,10 @@ function block_get_blocks_by_region($reg
   $build = array();
   if ($list = block_list($region)) {
     $build = _block_get_renderable_array($list);
+
+    // Allow modules to alter the region, either via
+    // hook_block_region_REGION_alter() or hook_block_region_alter().
+    drupal_alter(array("block_region_{$region}", 'block_region'), $build, $list, $region);
   }
   return $build;
 }
@@ -346,6 +350,13 @@ function _block_get_renderable_array($li
       '#weight' => ++$weight,
     );
     $build[$key]['#theme_wrappers'][] ='block';
+
+    // Allow modules to alter the renderable block array, either via
+    // hook_block_render_KEY_alter() or hook_block_render_alter().
+    // @todo D8: Inconsistent with other renderable array alter hooks; the alter
+    //   hook should be hook_block_*view*_alter() here, but we already use that
+    //   elsewhere.
+    drupal_alter(array("block_render_{$key}", 'block_render'), $build[$key], $block, $key);
   }
   $build['#sorted'] = TRUE;
   return $build;
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.959
diff -u -p -r1.959 system.module
--- modules/system/system.module	5 Sep 2010 02:21:38 -0000	1.959
+++ modules/system/system.module	10 Sep 2010 17:53:23 -0000
@@ -2013,6 +2013,14 @@ function system_block_view($delta = '') 
 }
 
 /**
+ * Implements hook_block_render_KEY_alter().
+ */
+function system_block_render_system_help_alter(&$build) {
+  // Remove contextual links from help block.
+  unset($build['#contextual_links']['block']);
+}
+
+/**
  * Implements hook_preprocess_block().
  */
 function system_preprocess_block(&$variables) {