When it comes to creating a forum for your blog, there you several choices available to you. You could always use phpBB, or even pay for VBulletin, but this might not be ideal if you are trying to integrate it with an existing WordPress blog.
If you’d like to try a popular alternative, I recommend you check out the RS Discuss WordPress plugin. With this plugin, you can easily add a simple bulletin board forum to your WordPress blog. You will then get all of the functionality of a regular forum, including the ability to set administrators/moderators. Other benefits include multiple language support and an RSS feed that users can have to monitor your forums.
The only major downside I’ve found with this plugin is that it requires you to allow user registration on your actual blog. I’ve also seen it mentioned somewhere that the current version of this plugin may have problems with the WordPress 2.3 tagging system.
Otherwise, you should have everything you need!
Update: If you find RS Discuss isn’t for you, check out this post which covers integrating a forum with WordPress. The post covers a variety of different forum options and provides a lot of useful information associated with it.
Kyle Eslick
Kyle Eslick is the founder and primary author of WordPress Hacks. You can learn more about him at KyleEslick.com or you can follow his personal tweets here.
Nice, best post I found on the subject.
If you add code of a full page template using your code ...
best collection 
Does anyone have problem after updating? in my case, my Visitor map doesn't work well after updating >.< 
very nice theme, but what exactly means wp 2.7 ready? is it compatible with the newest version of wordpress? get ...
14 feature in theme looks quite interesting but yet have problem on SEO with some theme of Wordpress. 
Nicen themes, good work :) 
When I click on that link I get this message:
Forbidden
You don’t have permission to access /blog/wordpress-plugins/rs-discuss/ on this server.
This is a really informative post … do you know how to add a Job Board as a Plugin to a WordPress Blog?
I want to add a forum to my blog, but I don’t want to include it in the same page style, I’m wondering if it’s possible to make a page that when I click on the Forum page, people are redirected to a new page with different design, which is a forum under my blog at http://www.benjamincip.com/forum for instance. I haven’t seen any information about it yet…
When I try to get to the plugin I get a forbidden error and when I try to go to the link about integrating a forum into wordpress I get an error from my web browser about trojans.