The plaintiffs' opening appellate brief in Baldwin v. Sebelius is due by the end of today at the Ninth Circuit. Although the plaintiffs have challenged the constitutionality of the minimum coverage requirement, that will not be at issue before the Ninth Circuit. Rather, the only issue will be one of justiciability, as the District Court held that the plaintiffs lacked standing (as their alleged injuries were not sufficiently imminent). To my knowledge, it will be the first brief filed in any of the courts of appeals in a case challenging the ACA's constitutionality. I will post a copy of the brief here as soon as it is docketed on PACER.
UPDATE: You can find the brief here. Despite the fact that the District Court never reached the merits, the brief does argue (at length) that the individual mandate exceeds Congress's enumerated powers. Interestingly, it also asserts that the very reason Congress specified that the individual mandate would not go into effect until January 1, 2014, was to attempt to deprive potential plaintiffs of Article III standing to challenge 1501(b). We have seen hundreds of contentions in these various cases, but I believe this one is genuinely new.
UPDATE 2: Because the appellants filed their brief on Wednesday, November 24, the United States's brief will now be due December 22.