Two of the developers of phpBB have announced a service called Forumatic that appears to be modeled along the lines of wordpress.com:
My opinion? It's a good start, but at best it's only a start. Forumatic looks great if you have a very small forum, not so great if you have a larger one and must pay the (IMO) exhorbitant prices. To me it looks perfect for a test board where you can try out the newest versions of phpBB without having to create a test board on your own site. Forumotion has nothing to worry about for now, but as Forumatic improves its services (and drops its prices), it could become a threat to forumotion's very existence.