phpMyForum is an very powerful freeware forum,
Some features:
-Design individually adaptable
-board code as HTML replacement
-email notification with new contributions
-private messages
-...
StickyBoard is an efficient, standards-compliant web forum, providing useful and intuitive features, while lacking extraneous bloat. The underlying code driving the forum is written in PHP, utilizing PEAR coding standards with XHTML and CSS output.
ScareCrow is meant to be a richly-featured and free alternative to commercial web message boards. The storage system is easily expandable to add new features to the code easily for programmers, while simple site owners can find all they need in web-base
Forum Plus! is a project which involves the developent of an ASP based bulletin board. Completely written from scratch to ensure maximum performance and a comprehensible code, the forum is gradually improving every day.
A wiki which is reprogrammable by its community. Allows the wiki community to collaboratively edit the wiki sourcecode in a similar way to how they write the textual content. Project activity mode: coma ( http://bayleshanks.com/pamv1 )
Geeklog Experemential Code and Plugins is for testing the bounds of possiblity with the geeklog code base as well as experemential versions of modified plugins that may be avaliable elsewhere. One focus is the Addicti0n experemential fork of Geeklog.
FoxFe Story Server is a collection of code comprised of a backend story server, a few frontend clients, and some intermediate code to allow the development of custom clients as needed.