MyBB

MyBB is an open source forum application. MyBB forked from XMB Forum in 2002.

From administration to posting a reply, MyBB is a forum package full of useful and to-the-point features for both you and your visitors, helping you to make running your bulletin board as easy as possible.

Features:

Rad Community: MyBB's friendly community will help you get your community started.
Extendable: Hundreds of plugins and themes make adding new features or a new look easy.
Simple to Use: MyBB offers an extensive range of features in an intuitive interface.
Multilingual: Community-maintained translations are available for more than 30 languages.