In case anyone else might find this useful, I've just written a tiny addition to this plugin to display the name of the forum that each recent topic is part of.
// GET FORUM WHICH POST IS IN - Phil Ewels, 26/09/2010
$sql_query = "SELECT * FROM phpbb_forums WHERE forum_id=" . $topic->forum_id. " LIMIT 1";
# Run Query
if ($prt_phpbb_dbinsecureon == "1") {
$forum = $phpbbdb->get_row($sql_query);
} else {
$forum = $wpdb->get_row($sql_query);
}
echo "<br /><small>" . $forum->forum_name . " </small>";
This should be inserted into display.php, around line 175 - 185, depending on where you would like the text to be displayed.
Please note that you may need to replace phpbb_forums with the name of the phpBB forums table in your database.