There are many plugins for WordPress , which are created in order to add functionality to your blog offline. We have compiled a list of six plug-ins with links to download, to install the forum on the WordPress blog.
1. bbPress
This plugin is from the creator of WordPress. So this one is very reliable and easy to use with WordPress.
2. Mingle Forum
Mingle Forum – allows you to set up a forum on your WordPress blog easily and quickly.
3. Simple: Press
Simple: Press – a very fancy and totally compatible plug-in forum for WordPress.
4. Tal.Ki Embeddable Forum
Tal.ki Embeddable Forums – this is the easiest way to add a forum, message board or discussion on your blog.
5. Zingiri Forum
Zingiri Forum – is a plugin that integrates myBB bulletin board with your WordPress blog. It will allow your readers to use the forum in easy way.
6. Wp2BB
Wp2BB integrates your WordPress blog and your phpBB forum. This plugin automatically creates a new thread in the forum for each new post on the blog.