don't hesitate to tell me to shut up and stop posting geek stuff. i just like playing with free software. here we go...
if you are going to use a content management system like joomla (i prefer xoops, but both seem to work well. are you using joomla?) why not use it for everything? integrate your forums into joomla. instead of using two seperate programs. but maybe you like using phpbb on it's own instead of module form inside of joomla, that's possible. anyway, i did a quick look around the phpbb site and found this:
an rss content syndicator. with this you can create your own rss feed based on the content generated in your very active forums. it will most likely add a few more hits to your site and if you have members who like to use rss they'll be happy too.
i did a quick look around the joomla site and didn't find a simple explanation on how to set up your own rss feed but i did notice that joomla.org did have rss available on their site, so i'd guess it's built in and you'd find the controls in the administration menu if it's not a separate module. it shouldn't be difficult. go to http://forum.joomla.org/
and scream help. i've done it with xoops and it's very very easy.
as always back up your database and do a complete directory backup before playing around! i've lost tons of work before because i thought i knew more than i really did. backups are our friend.
here's my feed.
sorry i didn't give great instructions but i don't use the same cms as you but the general ideas are the same. good luck!