First quick go at a Messages block. Needs polishing but seems to work.

blocks/messages/block_messages.php

@@ -0,0 +1,62 @@
+<?PHP //$Id$
+
+class block_messages extends block_base {
+    function init() {
+        $this->title = get_string('messages','message');
+        $this->content_type = BLOCK_TYPE_TEXT;
+        $this->version = 2004122800;
+    }
+
+    function get_content() {
+        global $USER, $CFG;
+
+        if ($this->content !== NULL) {
+            return $this->content;
+        }
+
+        $this->content = new stdClass;
+        $this->content->text = '';
+        $this->content->footer = '<a target="message" href="'.$CFG->wwwroot.'/message/index.php" onclick="return openpopup(\'/message/index.php\', \'message\', \'menubar=0,location=0,scrollbars,status,resizable,width=400,height=500\', 0);">'.get_string('messages', 'message').'...</a>';
+
+        if (empty($this->instance) or empty($USER->id)) {
+            return $this->content;
+        }
+
+
+        $users = get_records_sql("SELECT m.useridfrom as id, COUNT(m.useridfrom) as count,
+                                         u.firstname, u.lastname, u.picture 
+                                       FROM {$CFG->prefix}user u, 
+                                            {$CFG->prefix}message m 
+                                       WHERE m.useridto = '$USER->id' 
+                                         AND u.id = m.useridfrom
+                                    GROUP BY m.useridfrom");
+
+
+        //Now, we have in users, the list of users to show
+        //Because they are online
+        if (!empty($users)) {
+            foreach ($users as $user) {
+                $this->content->text .= '<div style="text-align: left; font-size: 0.75em; padding-top: 5px;">';
+                if ($user->picture) {
+                    if ($CFG->slasharguments) {
+                        $imgtag = '<img src="'.$CFG->wwwroot.'/user/pix.php/'.$user->id.'/f2.jpg" style="height: 16px; width:16px; vertical-align: middle;" alt="" /> ';
+                    } else {
+                        $imgtag = '<img src="'.$CFG->wwwroot.'/user/pix.php?file=/'.$user->id.'/f2.jpg" style="height: 16px; width:16px; vertical-align: middle;" alt="" /> ';
+                    }
+                    $this->content->text .= $imgtag;
+                } else {
+                    $this->content->text .= '<img src="'.$CFG->pixpath.'/i/user.gif" style="height: 16px; width:16px; vertical-align: middle;" alt="" /> ';
+                }
+                $this->content->text .= '<a href="'.$CFG->wwwroot.'/user/view.php?id='.$user->id.'&amp;course='.$this->instance->pageid.'" title="'.$timeago.'">'.fullname($user).'</a>';
+                $this->content->text .= '&nbsp;<a target="message_'.$user->id.'" href="'.$CFG->wwwroot.'/message/user.php?id='.$user->id.'" onclick="return openpopup(\'/message/user.php?id='.$user->id.'\', \'message_'.$user->id.'\', \'menubar=0,location=0,scrollbars,status,resizable,width=400,height=500\', 0);"><img height="11" width="11" src="'.$CFG->pixpath.'/t/message.gif">&nbsp;'.$user->count.'</a>';
+                $this->content->text .= '</div>';
+            }
+        } else {
+            $this->content->text .= "<center><font size=\"-1\">".get_string("nomessages")."</font></center>";
+        }
+
+        return $this->content;
+    }
+}
+
+?>

lang/en/message.php

@@ -17,6 +17,7 @@
 $string['mycontacts'] = 'My Contacts';
 $string['newsearch'] = 'New search';
 $string['nosearchresults'] = 'There were no results from your search';
+$string['nomessages'] = 'No messages waiting';
 $string['offlinecontacts'] = 'Offline Contacts ($a)';
 $string['onlinecontacts'] = 'Online Contacts ($a)';
 $string['onlyfromme'] = 'Only messages from me';