WebSite+Forum+login

Well hello im in the process of making a new website.The website will include tutorials/guides/how-to's on various Unix platforms (mainly BSD). Now i have a could of ideas and know what i want and would like to use. Here are some sites that gave me ideas and inspiartion:

http://bsdguides.org/guides/freebsd/webserver/apache2_install.php
If you browse the site you could see that you could respond to the guides posted and make any comment/suggestions.

I would like to have that option with the site.
Now as for the forum i would like to use phpbb
http://www.phpbb.com/
Now i would like to have the users that use the forum to use the same login to reply/post to the guides section of the site.

It's very simple but then main thing/problem i'm having if having the too login systems work as one. How would i do this? or is there something like this already or a mod for phpbb to do this? If you would like to help i would also appreciate that also.
This is All open-souce and free.
Thank You very much for any suggestions/comments.

http://www.cpgnuke.com/

Very good/secure CMS Portal, has built in phpbb forums & many other great features. 1 login for users & 2 for admins.