ThreadBuddy

The Thread Buddy is a threaded discussion tool that uses wildcard DNS, so you can pick your own discussion URL. The thread is tied to the *.threadbuddy.com URL that you choose, so there are endless open "channels" to use. The thread buddy is search engine friendly since it has an integrated plaintext and rss feed. Also, the thread buddy can easily be integrated into any site. See the help page for how to integrate a Thread Buddy into your site.