Almost everybody was surprised by the $53 million Paranormal Activity 3 took in over its opening weekend, including the movie's producer Jason Blum. ''I was floored,'' he says. ''I got an email from [Dimension chief] Bob Weinstein on Friday: 'Congratulations: 35-40 [million].' And then Saturday he wrote me, like, 'Okay, this is disgusting.''' Blum, who also oversaw this year's other megasuccessful low-budget horror flick, Insidious, hopes to keep the momentum going: He's currently test-screening director Barry Levinson's found-footage eco-terror film The Bay (''Definitely the most graphic horror movie I've ever been involved with''); he just wrapped another frightfest, Sinister, starring Ethan Hawke and Juliet Rylance (''I think we have a new take on an old tale''); and he's hard at work on director Rob Zombie's latest yarn, The Lords of Salem (''It's contemporary but, basically, imagine the women they killed in the Salem witch trials actually were witches''). Then there's Area 51, director Oren Peli's long-awaited directorial follow-up to the original Paranormal Activity. ''We're still tinkering with it,'' Blum says. Of course, given Paranormal Activity 3's triumph at the box office, it surely won't be long before Blum's attention turns to a fourth Paranormal installment. ''We really haven't started thinking about it yet,'' he says, laughing. ''We're going to enjoy [PA3's success] for a second.''