Try the Early Development Version of the bbPress Plugin
Progress on the bbPress plugin continues, though it’s been slower than expected with missed deadlines. However, the “super-pre-alpha” version is available for testing, if you are stout of heart. The team could certainly use any help you can lend with bug reports and testing.
Download the plugin from: http://trac.bbpress.org/browser/branches/plugin. Scroll down to the bottom of the page and you’ll be able to download the zip archive. This is by no means recommended for a live site, but it’s something to work with if you’re a bbPress enthusiast and you like living on the edge. More information about the development process can be found at the bbPress forums.