This Beta Sign Up Form is where to register beta codes received at BlizzCon '08 so that Blizzard can send word on how to become a beta tester for when the time comes, though what game this will be for or when this will happen are not specified. And this may not be for a while, as they say: "Be advised that it may be quite some time before this beta test begins, and this sign-up may not be for the next beta test to become available." Thanks Joystiq.