Caught in the Act

07/12/2006 at 06:00 AM EDT

• Mary-Kate Olsen, dancing with a scruffy-faced guy to Michael Jackson's "Billie Jean" at New York City hot spot Marquee during a party for model May Anderson. And when Olsen didn't have her arms around her pal, she was smoking cigarettes and sipping an energy drink. Nearby, Jamie-Lynn Sigler hung out with boyfriend Scott Sartiano – Ashley Olsen's ex – and the following night, Leonardo DiCaprio and girlfriend Bar Rafaeli partied at the club.

• Hilary Duff, grabbing food with boyfriend Joel Madden and his mom at the Arizona Pizza Company in Leonardtown, Md. The actress signed autographs between bites of pasta and pizza but politely refused to pose for photos.

• Patricia Arquette, gushing about her "perfect" Venice wedding at the Monte Carlo TV Festival. "It was incredible from the first second," she told us about her nuptials to new husband Thomas Jane. "It felt so right, and so easy. Our whole life is a honeymoon."

• Lindsay Lohan and Nicole Richie, snapping pictures of each other with a digital camera at the grand opening of Social Hollywood. Also making the scene at the L.A. club: Charlize Theron, Jamie Foxx and Ivanka Trump, who got on the dance floor for Usher's "Yeah!"

• Jessica Alba, snuggling with boyfriend Cash Warren (who wore a T-shirt that read "Champagne Taste on a Beer Budget") at L.A. hot spot Hyde.

Owen Wilson

Spirit Pictures / WENN / Landov

• Mena Suvari, being the first celebrity to get booted after only 30 minutes of play in the World Series of Poker Ladies Event at the Rio hotel in Las Vegas. Other stars who tried their hand on the all-celeb Hollywoodpoker.com Diamonds team: Anne Heche, Mimi Rogers and Kelly Hu.

• Owen Wilson, making the rounds at the Tropicana Bar in Hollywood. The Me, You and Dupree star hung out with record honcho Jimmy Iovine and left with a CD in his hand. Wilson's Dupree costar Kate Hudson was also there having a girls' night out with pals.

• By JED DREBEN, LAURA HAHN, MARION HIXON, JULIE JORDAN, JEFFREY SLONIM and NANCY WILSON