How do you allow a user to set the audience of a node to any Organic Group without giving them the "administer nodes" permission?
I created a patch to the Organic Groups module to add the "administer audience" permission.  The patch can be found here, http://drupal.org/node/1211974

Here's the patch inline, 

diff --git og.module og.module
index 38cc452..0206115 100644
--- og.module
+++ og.module
@@ -558,7 +558,7 @@
  * Implementation of hook_perm().
  */
 function og_perm() {
-  return array('administer organic groups');
+  return array('administer organic groups', 'administer audience');
 }

 /**
@@ -1833,7 +1833,7 @@
   }

   $node = $form['#node'];
-  $required = variable_get('og_audience_required', 0) &amp;&amp; !user_access('administer nodes');
+  $required = variable_get('og_audience_required', 0) &amp;&amp; !user_access('administer nodes') &amp;&amp; !user_access('administer audience');
   $is_optgroup = FALSE;

   // Determine the list of groups that are shown.
@@ -1843,7 +1843,7 @@
   foreach ($subs as $key =&gt; $val) {
     $options[$key] = $val['title'];
   }
-  if (user_access('administer nodes')) {
+  if (user_access('administer nodes') || user_access('administer audience')) {
     // Node admins see all of groups.
     $all = og_all_groups_options();
     $other = array_diff_assoc($all, $options);
@@ -1900,7 +1900,7 @@
   elseif (!empty($gids)) {
    // populate field from the querystring if sent
    $groups = $gids;
-   if (!user_access('administer nodes') &amp;&amp; $simple) {
+   if ((!user_access('administer nodes') &amp;&amp; !user_access('administer audience')) &amp;&amp; $simple) {
      // filter out any groups where author is not a member. we cannot rely on fapi to do this when in simple mode.
      $groups = array_intersect($gids, array_keys($options));
    }
@@ -1949,7 +1949,7 @@
     // show multi-select. if less than 20 choices, use checkboxes.
     $type = $cnt &gt;= 20 || $is_optgroup ? 'select' : 'checkboxes';
     $max_groups = variable_get('og_max_groups_'.$node-&gt;type,'');
-    $description_max_groups = ($max_groups &amp;&amp; !user_access('administer nodes')) ? format_plural($max_groups," Limited to !max_groups choice."," Limited to !max_groups choices.", array('!max_groups' =&gt; $max_groups)):'';
+    $description_max_groups = ($max_groups &amp;&amp; !user_access('administer nodes') &amp;&amp; !user_access('administer audience')) ? format_plural($max_groups," Limited to !max_groups choice."," Limited to !max_groups choices.", array('!max_groups' =&gt; $max_groups)):'';
     $form['og_nodeapi']['visible']['og_groups'] = array(
       '#type' =&gt; $type,
       '#title' =&gt; t('Audience'),