WOMEN willing to go head-to-head with Cameron Diaz still have a chance with her latest fling, John Mayer. Though he's been spotted around town with the leggy blonde lately, an insider dishes that the two are "definitely not exclusive . . . He takes non-famous girls to dinner at low-key restaurants all the time. He doesn't like having the paparazzi all over him." Another insider confirmed, "Jessica Simpson [Mayer's ex] used to call photographers and set him up all the time. He tries to shy away from it. John and Cam aren't official . . . he's still on the market."


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BALD pop wonder Sting and bushy-haired actor Denis Leary are having a hair-off. Leary tells blackbookmag.com, "Sting called me a c- - -. I said something about his hair, or lack thereof, and he called me a c- - - and said that when I got older, we should compare hair. And I'm like, Let's go! I'm 50! Let's go!" Leary's memoir, "Kiss My Irish ***," comes out next year.

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ALEX Rodriguez took a break from the AL East pennant race last night to play the role of spectator at the U.S. Open. It was love-love for A-Rod and his wife, Cynthia, as they held hands and cuddled courtside while watching the Nicole Vaidisova-Sharar Peer match at Arthur Ashe Stadium. Asked by The Post's Dan Kadison what it was like to be in the crowd instead of on the field for a change, the Yankee slugger said, "It's always nice." The couple later moved up to the USTA Presidential Box with NBC anchorman Brian Williams.

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TARA Reid gets mocked for her hard partying and bad plastic surgery, but she has a loyal defender in Constantine Maroulis, the "American Idol" alum. "I went to high school with Tara Reid," Maroulis recently told Baird Jones. The two grew up in Wyckoff, N.J. "I noticed her even be fore high school because she also went to a private Catholic grade school," Maroulis said. "She was so striking with that hair and she was pretty developed even when she was a little kid . . . She was always a good girl, a sweet kid. It's tough, when you are making a name in Hollywood with the press, the way people brand you. People are unfair to her. Compared to the other party girls - Nicole, Paris, Lindsay - Tara doesn't look so bad these days. Tara did not go to prison, she never broke the law. Tara is trying to clean up her act. She is a talented girl."

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Britney Spears was between a rock and a hard place in Las Vegas.

The dramatic divorcée showed up at a Sin City night club grand opening party on Friday night sporting a huge diamond rock on her left ring finger - the traditional spot for engagement bands.

"I couldn't believe what I was seeing," said one onlooker.

"She marched in with her security guards displaying the stone to everyone - either she's about to do a Vegas wedding again and get hitched, or she's just too dim to realize where she put the ring."

Fueling the rumor mill, the blond-wigged pop tart was later spotted getting up close and personal with magician Criss Angel in the VIP room at LAX club in the Luxor Hotel and Casino.

A source close to Angel - a Long Island native whose estranged wife accused Cameron Diaz of busting up their marriage - said there's definitely no marriage plans in their future.

"They met to talk about performance stuff and anything Criss could do to lend a hand," said the source. "That's the extent of it."

It wouldn't be Spears' first relationship shocker in Sin City.

She married childhood friend Jason Alexander in 2004, but had the marriage annulled before the ink was barely dry on the wedding certificate.

As guest of honor at LAX's opening, Spears, dressed in a white baby-doll dress and fedora, had been expected to perform.

But despite the hype surrounding her new single "Gimme Gimme," she remained in the VIP section of the club for the duration of the event.

The crowd saluted the star when she arrived flanked by security.

A reveler said, "She was kind of hard to see because there were a lot of security around her. But when she arrived, the deejay turned down all the music and said, 'We have a mega-superstar for the grand opening of LAX . . . Britney Spears!' "

The crowd went wild cheering for Britney, according to the source.

"After that, they played her new song. She danced a little bit with Criss Angel, who was right next to her. At one point, he kissed her hand, but that was as much as we saw," said the source.

"She stood up and danced for a little bit when 'Billie Jean' was on," said a mole.

At 2 a.m., the star and her friends left the club flanked by more than 10 security guards.


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Lindsay Lohan will be looking good in case there are any more "exclusive" photos of her in rehab. A spy in celebrity hairdresser Ken Paves' salon said, "Ken sent someone out to Utah to do Lindsay's extensions this week." Lohan was the subject of an OK! magazine "exclusive photo shoot" several weeks ago that wasn't sanctioned by the starlet. "Someone on the premises of the rehab took pictures of her and sold them. She didn't know about it, and it was a violation," a friend said. A rep for Lohan didn't know about her hairdressing.


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BRITNEY Spears' ex-assistant Shannon Funk not only sold her down the river by giving an exclusive to OK! Magazine about the singer's odd behavior, but Funk is doing all she can to be famous in her own right. The unemployed blonde showed up at Body English in Las Vegas earlier this week and made a beeline for Jeff Beacher and comic Jamie Kennedy. According to our spy, "She walked right over, flashed her [breasts] and started aggressively trying to make out with Jamie. She got someone to take a picture with her and Jamie kissing and then stayed for two more minutes and bolted with the pics. We're all waiting to see which weekly magazine she sells them to."