user blogging and discussions

Hi,    I'm in the process of building a website using RoR and would like to add the capability to allow registered users of my website create personal blogs on my site as well as start/participate in discussions (discussion forums).

I took a look at some of the blogging engines out there like typo and mephisto and it looks like those are geared more towards helping *me* as the developer of the website, add a blog section to the site where I can publish my own content (correct me if I'm wrong here).

Are there blogging platforms (either open-source or commercial) and discussion forum platforms out there for Ruby on rails, that I can integrate with an existing application, without disrupting / taking over my existing databases and functionality, that will help with User Generated Content (UGC).

The famous 15 minute blog demo on the RubyOnRails website does come to mind i.e. I could just build it myself, but a platform that's been tried-and-tested and provides features like spam protection, RSS syndication among other things would be great. Any help here much appreciated.

thank you, Gautam