NewsQueryFU (NQFU)

Cameron Diaz has dipped back into the musician well to find herself a new guy — John Mayer! The 34-year-old Shrek actress, whose almost 4-year relationship with Justin Timberlake ended in January, and rocker Mayer were spotted out in New York last night, a source exclusively tells Usmagazine.com. “They went out to several places…It was the two of them, getting to know each other, out on the town.”

According to a source, Diaz, who is in New York filming the comedy What Happens in Vegas, and Mayer have known each other for awhile. “This was technically not their first time hanging out…they’ve hung out together with friends before. But this was the first time together like this. It’s new and developing…but they really like each other and it went well,” a source explained.

A rep for John Mayer would not confirm the new couple, telling Us, “We do not comment on our client’s personal lives.” Diaz’s rep also had no comment.

Earlier today, Mandy Moore debunked a rumor that she was seeing Mayer, 29. She chalked it up to friendship, but in light of these new developments, maybe she feared the wrath of Cam!

Jessica Simpson’s new color is green.

A source close to the singer tells Us Simpson is “really jealous” that ex John Mayer is seeing Cameron Diaz. “She had her mouth open a mile wide when she found out,” says the source. “She just freaked.”

Simpson, 27, parted ways with Mayer, 29, in May after dating him on and off for seven months, and “she thinks about him all the time,” says the source. “She is so not over him.”

Meanwhile, Simpson seems to be a distant memory for Mayer, who has continued his summer romance with Diaz, 35, in NYC. Though they spent August 22 and 23 apart (he hit the gym and recorded at a studio; she shopped and then lunched at Mary’s Fish Camp), they finally squeezed in quality time in the wee hours of August 24 at hot spot Socialista. The pair — who left at 4 a.m. through different exits — “were very cozy,” says a witness.

Echoes a source close to the new couple, “They’re happy.”