As far as i know there are not any templates for discussion pages, you could always download a pre built forum such as phpBB from the internet, it runs on php, and uses mysql databases, its also very easy to set up.
I use Dreamweaver daily. Have to agree there are no templates for a forum in Dreamweaver. Your best bet as ChrisG4620 says is to go with something like phpBB which is very easy to set up and run. The last time I looked into and used phpBB it had some security issues needing to be sorted out.
Another very good option is a Wordpress site "No longer needs to be a blog" with a forum plugin. There are a few forum plugins one of which was pretty powerful and easy to use. I can't remember the name right now but will check when I get home from work.