Assuming that your phpBB and Drupal installations share the same database, this code will connect to the phpBB topic table and display the 10 latest posts.

If you have any forum sections that you would not like included in the list, be sure to exclude them in the SQL, like forum_id 9 is in this example.

<?php 
$sql = "select topic_id, forum_id, topic_last_poster_id, topic_title  from phpbb_topics where forum_id != 9 order by topic_last_post_time desc limit 0,10";
$result = db_query($sql,array());
print "<ul>";
foreach ($result as $row) {
  print "<li><a href=\"http://www.example.com/viewtopic.php?f=$row->forum_id&t=$row->topic_id&start=$row->topic_last_poster_id\">$row->topic_title</a></li>";
}
print "<ul>";
?>