I am developer working on implementing your Active Forums module one of my clients.

We are setting up multiple forum pages on a DNN site. One of the forum pages will be a mailing list, and so it will only be a single forum that people will want to subscribe to, and it looks clunky that they have to drill down to get the forum when there is nothing else there. Is it possible to make a certain forum the "default" forum for that page, so that it will go straight to the forum page, so they don't have to pick it from the forum list? Our main goal is that we want the users to be able to see the "Subcribe" checkbox as soon as they land on the page, because they won't go looking for it.

I am not sure which edition of Active Forums you are using, but Active Forums Enterprise includes a module called ActiveForumViewer. I believe the Forum Viewer would be able to display a single forum as you have described.