I had it from the owners of the SPSP Forum that it is up and operational again. However, I have heard from a number of people that it is not functioning for them. The powers that be have been informed and are working on the issue however, I have no idea when it might be resolved.
If the embedded link does not work, the URL is http://forum.paymentsecuritypros.com/.
I am glad to have this resource back and look forward to people getting back into the swing of using the Forum.
UPDATE: I wish I could tell you that this resource is going to be functional sometime soon, but I have no idea if it will. I am very sorry that the Forum no longer functions. I can only hope that people resolve their issues and the Forum can be the premier resource for PCI knowledge.