phpBB is a free and open source forum bulletin board software that can be used to stay in touch with a group of people or can power your entire website.
bbPress is one of the widely used open source forum scripts by the makers of WordPress. This is very similar to WordPress.
Say good bye to the old, cluttered and cumbersome forum interfaces. Our Forum software has a fresh UI which is simple, clean and impressive with an advanced and powerful engine underneath.
3. Invision Power Board
Another popular paid forum software. When ever vBulletin is compared it is compared to Invision Power Board.
Undoubted vBulletin is the best forum software. With its years of experience and great support has made it the best forum software. vBulletin is paid forum script but it is worth to its value.
PunBB is a fast and lightweight PHP-powered discussion board. It is released under the GNU General Public License. Its primary goals are to be faster, smaller and less graphically intensive as compared to other discussion boards.
FluxBB is a fast, light, user-friendly forum application for your website. FluxBB was designed as a lighter, faster alternative to some of the traditional feature heavy forum applications.