Not sure if this is the correct place for this, but I wanted to let others know of a plugin that can connect the users of phpbb3 with WordPress (or WPMU).
I'm currently developing this plugin, so it is listed as beta. Despite that, it appears to be stable currently, as I am using it on another site where I integrate WordPress, WordPress MU and phpBB3 and the users are synchronized between all systems.
I plan on adding more functionality at some point in the future, so any additional feedback on it would be appreciated. Also, if you know php, WordPress and/or phpbb3, any additional programming suggestions would be very helpful.