The private respondents--the National Federation of Independent Businesses, Kaj Ahlburg, Mary Brown, and the recently added Dana Grimes and David Klemencic--have filed their two brief (due today) in HHS v. Florida (No. 11-398). One addresses the constitutionality of the minimum coverage provision, and the other addresses the applicability of the Anti-Injunction Act.
You can access their brief on the constitutionality of the individual mandate here.
And you can access their brief on the AIA issue here.
As a reminder, three other briefs are due today: (1) the State Respondents' brief on the minimum coverage provision, (2) the State Respondents' brief on the Anti-Injunction Act, and (3) the United States's brief on the Anti-Injunction Act.
UPDATE 1:30 PST: Now just waiting on the United States's brief.