Discus Freeware is the best choice for webmasters who need simple message board capabilities. This free product provides basic framework to post, search, and receive e-mail notification. It also includes an extensive tool set for administrators to manage discussion. Discus Freeware can also be upgraded to Discus Professional at any time.

pureBB is a fast and reliable discussion board with a mySQL database backend. This forums has many features, and many more to come as this is in constant development.

CGIForum is an attempt to build a good, light-weight, free forum

The following new features have been added comparing with Atlant Lite version:
Fee Based Membership Sign Up. Script supports fee based membership sign up with real-time credit card processing. When membership period is expired, user has an ability to update their membership subscribing by using fee based membership updating service. For real time credit card verification and processing the Clickbank.Com company is used, but other such on-line billing companies can be used as well. Admin has an ability to add/edit new membership profiles via web admin interface.
Messages Moderating. Optional moderating of messages submissions by an administrator: the administrator has the ability to look through messages from a special form, analyze messages information and make a decision about submitting messages to the index or deleting messages from that form; All this should be done before messages appear in the index

The ActiveBoard is a powerful, multi-threaded, easy to use, easy to navigate and fully customizable message board system.