Some weeks ago Jussi asked about how to go about intagrating a forum with one's WikiServer. I thought this was a brilliant idea - a forum is actually much more useful for many environments than a blog or even a wiki. I think the concept of collaborative editing is quite foreign for the majority of existing companies and blogs are very often just silly. A discussion however is something that everyone is used to with email and group addresses yet everyone knows how painful it is to create “workgroups” - a group of people working on the same thing - which is exactly what a discussion group/forum is meant for.
There's obsiously no shortage of great free/open source forum applications out there. My first recommendation was Vanilla due to it's very lightweight nature, but it quickly dawned that it's not really the right choice.
My next choice is PunBB which we've run very successfully on the Estonian Macintosh User Group. It has all the important features, is fast and just “quick and dirty” enough to make your own modifications to it. It's also more secure than phpBB and gives excellent performance even with large installations.
The next and biggest question in integration is of course authentication - we don't want to manually create all the wiki server accounts in the forum software. The ideal solution would be to have the forum share the same session with the wiki software - a kind of SSO solution. This would be awesome but not really feasable at this time. The next best thing would be to have PunBB authenticate against the same LDAP server as the wiki. This something that PunBB doesn't yet do.
So I threw together a little extension for PunBB that enables LDAP authentication. You can download it from my Github page. Once you have PunBB and the extension installed, it's simply a matter of editing the respective templates to include the links to both applications.
One thing to note - PunBB doesn't, AFAIK, have a notion of a completely “private” bulletin board. That means, as is, the solution is not appropriate if your wiki is publicly accessible.