Free forum/Community builder software

Look beyond vBulletin. If you are planning to add a forum or bulletin board to your site and don't want to spend a lot on the platform, the good news is that there are a lot of free alternatives available. Here are a few listed below, leave a comment if I have missed out on something.     

SMF

A free community software based on PHP and MySQL. Complete feature list -

http://www.simplemachines.org/about/features.php

phpBB is one of the most widely used Open Source forum solution. Version 3.0 incorporates a professional-quality modular design, high security, multiple-language interface, support for a multitude of database servers and complete layout customisation, all with a low execution overhead. Complete feature set can be found here http://www.phpbb.com/about/features/

bbPress

From the creators of WordPress, bbPress is focused on web standards, ease of use, ease of integration, and speed. 

View live here http://bbpress.org/forums/

Beehive Forum

a PHP/MySQL discussion forum with frame-based layout, for easy navigation.

View live forum http://www.beehiveforum.net/forum/

Dolphin

Impressive community builder based on PHP/MySQL  With dolphin you can create dating sites, social networks, content sharing portalsThough free, it requires a fee of $39/yr if you want to remove the links to publisher.

IceBB

Powered by PHP and MySQL, icebb is a free and open source forum solution.

Try it here http://icebb.net/demo/

nextBBS

nextBBS is an open-source Internet forum system written in PHP and its currently running its public beta.

UseBB

UseBB is a light and Open Source PHP 4 and MySQL based forum package, distributed freely under the GPL license. 

Try it here -  http://www.usebb.net/community/forum.php?id=7

Vanilla

Vanilla is an open-source, standards-compliant, multi-lingual, fully extensible discussion forum for the web.