Open Source implementations of communities and forums

Recently found Pmwiki - a wiki based system made in PHP that can be used by an person interested in posting a web page , or communities . The page editting is really simple and various customizations can be made . Overall rating : A .

PmWiki HomePage

And of course there is also my personal favorite phpbb forums setup . This again is extremely lucid , customizable and contains almost all the features desired of such a software including email verification , customizing the templates etc . No wonder almost all the sites use this in their forum section .

PHPBB HomePage