Forums are back up, and secured better than before, so this shouldn't happen again. Knock on wood.
Answers to common comments we've received:
Yes, we know it was a phpBB hack.
Yes, I know it was my user account that was used to blast out the emails.
Yes, we know the IP of the hacker.
No, we don't want you to sign up for a free <insert crap here> to support our site.
Also, please note, we have never, ever sent out a mass email to our forum users so if you ever receive one, especially one that reeks of spam, know that it wasn't us, and it never will be. As such, the admin page that does the mass emailing has been deleted from our install of phpBB.
Sorry for the inconvenience. To make it up to you, we've finally installed the file attachment mod. Registered users can now upload up to 20MB of files, plus 2MB in their private messages.