Simple:Press forum
http://www.stuff.yellowswordfish.com/simplepress-forum/
It is excellent
You
1) install and enable it as usual
2) create an empty page with any name and sf-forum slug
3) configure the plugin (page, permalinks on 1st and last tab etc)
4) create a forum group and forums. Remember to choose access groups first if you want guest=no access, logged in=std access and so on)
5) start using it.
You might want to create a page template without a sidebar, so that you would have more space for a forum. You can run this forum beside a sidebar if you wish, though.
If you are running a multilingual blog (with Gengo) then Gengo must have auto-append language code = off or else there will be url trouble with this forum.
