WP-United integrates phpBB and WordPress to make a social site.
User integration: including single sign-on, synchronised profiles and avatars, and user management. Works with external registration modules such as social login plugins. Users in phpBB get accounts in WordPress and vice versa. Completely controllable and customisable by setting permissions for who can integrate and at what level, using a unique drag-and-drop interface.
Template integration: Have your phpBB forum appear inside your WordPress site. Or vice-versa; integrate your WordPress blog appear inside your phpBB header and footer. Includes a “one-click” mode that analyses your theme’s CSS and modifies it on the fly to avoid CSS and HTML conflicts. This is no iFrame solution, it is a complete and automatic template integration.
Behaviour integration: Use phpBB smilies and word censor features in WordPress
Cross-posting: Post something in WordPress and have it cross-posted to your forum — Automatically or manually, you choose! Once an item is cross-posted, comments in phpBB and WordPress can be set to sync up under the blog item too!
Widgets: A set of WordPress widgets that show information about your phpBB forum: Latest posts, latest topics, users online, forum stats and an integrated login/meta/avatar/profile widget.