Vanilla is a rather nice forum application with tons of extensions.
It is relativily easy to install on Redbrick. Also, if you have already installed Wordpress you can integrate the Vanilla logins with your Wordpress user logins (also check here if you want to also use your Wordpress template tags).
For the most part the instructions bundled with it are correct. However you will need to have an SQL account so if you don't have one email the admins.
I haven't tested any of the extensions nor the download updates (I suspect this won't work), but other than that it works quite well.