FluxBB

FluxBB is an open source forum application. Forked from PunBB in 2008, FluxBB is a popular lightweight forum application, powering forums for Arch Linux and μTorrent.

FluxBB is designed as a lighter, faster alternative to some of the traditional feature heavy forum applications. It is easy to use and has a proven track record of stability and security making it an ideal choice of forum for your website.

Features:

Easy to use: Simplicity is the key. Featuring a beautiful, clean interface, FluxBB is focused completely on ease-of-use and usability.
Blazing speed: FluxBB focuses on the most essential features a forum needs and comes without the bloat many other systems bring along, so that you can enjoy the speed.
Clean admin interface: Take full control over your forum, easily editing permissions, changing board-wide options and rearranging the structure of your forum.
Flexible permission system: FluxBB comes with a flexible permission system designed to give you full control over your user groups. Allow them to view different sections of your forum, give privileged users moderator status (multiple moderator groups are supported).
Powerful moderator tools: Administer your board with ease using powerful moderator tools to manage users, banning, censoring, reported posts, forums and topics. Do it yourself or delegate these tasks to moderators as you see fit.