I'm assuming you are planning on having your forum in it's own directory.
You can create a simple html page with a link to your forum.
OR do you want anyone who goes to your site domain to be redirected to your forum?
Eventually I plan to have a 'landing page', either wordpress or hopefully in the future xfadvanced.
The forum can always be moved to its own directory, but I would think about it now.
You can always make a redirect from your root to the forum to leave your options open.
That is what I'm going to do.