Httrack can mirror phpBB's very well in most cases, and I have mirrored lots of
them with it. If you use this as your scan rules it will block out most
everything except for the main topics and profiles.

-*tracker.php*
-*ignore.php*
-*download.php*
-*&watch=topic*
-*&unwatch=topic*
-*mode=reporttopic*
-*watched_topics.php*
-*search_id=dl&dl_status=*
-*privmsg.php*
-*posting.php*
-*rabbitoshi.php*
-*adverts.php*
-*ads_search.php*
-*search_author*
-*viewtopic.php?p=*
-*viewtopic.php&p=*
-*mark=forums*
-*mark=forums*
-*mark=topics*
-*&mark=topics*
-*printertopic=*
-*mode=unread&p=*
-*&postdays=0&postorder=asc&highlight=*
-*&view=previous*
-*&view=next*
-*&spmode=full&dl=names*
-*search_id=unanswered*