PunBB

PunBB is a fast and lightweight PHP-powered discussion board. It is released under the GNU Public License. Its primary goal is to be a faster, smaller (only 257KB) and less graphic alternative to otherwise excellent discussion boards such as phpBB, Invision Power Board and vBulletin. PunBB has fewer features than many other discussion boards, but is generally faster and outputs smaller pages.

Installation
Installation is pretty easy. The only thing you need to be aware of is that when it asks for the address to your installation, you need to input the correct address