The CloverfieldMovie.com website has been updated with the movie's rating - PG-13.
Also, the film credits (aka "billing") have been added to the site, and have been updated with additional info. I have highlighted the changes in bold. Notably, in addition to Double Negative, Tippett Studio is listed under Visual Effects.
PARAMOUNT PICTURES Presents A BAD ROBOT production 'CLOVERFIELD'
LIZZY CAPLAN, JESSICA LUCAS, T.J. MILLER
MICHAEL STAHL-DAVID, MIKE VOGEL, ODETTE YUSTMAN
Visual Effects by DOUBLE NEGATIVE and TIPPETT STUDIO
Costumes Designed By ELLEN MIROJNICK
Edited By KEVIN STITT, ace
Production Designer MARTIN WHIST
Director Of Photography MICHAEL BONVILLAIN, asc
Executive Producers GUY RIEDEL, SHERRYL CLARK
Produced By J.J. ABRAMS, BRYAN BURK
Written By DREW GODDARD
Directed By MATT REEVES