Just minutes ago MarketWatch reported;

Star Wars: Episode III -- Revenge of the Sith scored $50 million in first-day receipts at 3,661 theaters across the nation on Thursday, box-office tracker Exhibitor Relations said Friday. The take handily beats the one-day record of $44.8 million set last year by "Shrek 2." "Sith" is distributed by News Corp.'s (NWS) 20th Century Fox film unit.

Update:

Here's a report from Box Office Mojo on the the movie's North American box office:

After starting the day with $16,912,367 from midnight shows alone, Star Wars: Episode III - Revenge of the Sith closed Thursday with $50,013,859 from an estimated 9,400 screens at 3,661 theaters. That's the biggest day ever for a single movie in history.

"When I consider it's a Thursday with kids in school, I'd figure it can't do that," distributor 20th Century Fox's head of distribution, Bruce Snyder, told Box Office Mojo. "I did not think we could do $50 million. I was thinking maybe we could catch up to Shrek 2 on Saturday. I'm as surprised as the rest of the world."

For further perspective, the biggest opening weekend of the year thus far had been Hitch's $43.1 million, and Revenge of the Sith blew past that in one day. Sith's gross is surprising, in part, because the previous Star Wars installment, Attack of the Clones, had an opening day on par with The Phantom Menace and ultimately made significantly less. In 2002, Clones grossed $30.1 million on its way to $310.7 million, while Phantom earned $28.5 million en route to $431.1 million.

Hit the link above to read more and be sure to check our their Star Wars Special Briefing.