here's a site you might find helpful..
http://www.opensourcecms.com
They have many different forum solutions in which you can try before you... install!!
I personally don't like phpbb, but that's because phpbb is the most popular one and I've seen it just too many times. I've used phpbb off and on for years on different boards, and I personally believe that the "golden age" of phpbb is over.
I really like simple machines forum. In my humble opinion, I feel that SMF rocks!! SMF is easy to install, and easier to mod. If you want to install a mod for SMF, all you do is download it and click the install button. There's no need to edit files, like with phpbb. Another problem with phpbb, because of it's popularity, is that it's usually exploited and hacked the most. With any forum software, you really have to keep it updated to prevent harmful exploitations.