Spotted!

Aug. 10 in Las Vegas, R&B singer/songwriter Jeremih took over Jet Nightclub at the Mirage Hotel, during their popular weekly party, "Industry Mondays," where he performed a four-set concert for screaming fans. Thousands of partygoers jumped onto the dance floor when he began belting out his new hit single, "I'm A Star," which began climbing the major music charts last week. The Chicago native proceeded to serenade the ladies in the audience with an a cappella rendition of his summer breakout single, "Birthday Sex," followed by an up-tempo version of the hit that had everyone in the club singing along with him. "Crowd control was nuts, girls kept trying to reach out and touch him while attempting to jump on stage," mentioned a guest at Jet Nightclub. The R&B crooner has had little time to sleep this summer due to a rigorous summer tour schedule that has taken him from New Orleans to Las Vegas, where he gave Sin City's Monday night crowd a performance to remember.

Jordin Sparks at the 102.7 KIIS Fm’s Teen Choice Awards Lounge at the W Hotel in Westwood, Calif.

Ryan Cabrera at the Hornitos Lounge at The Underground in Chicago.

Jermaine Dupri chatting with Joy Bryant at the afterparty for Pete Yorn’s concert at W Chicago City Center.

Jamie Lynn Sigler and Jerry Ferrara sharing Lil Big Macs at STK New York.

Paul McCartney stopping by Rihanna's table at Philippe East Hampton where Rihanna was enjoying sea bass and chicken fried rice.

Hayden Panettiere, Zachary Levi, Joel McHale, Aimee Teegarden, Chevy Chase, Kathy Griffin and Padma Lakshmi attended NBC's TCA after-party in L.A. on Aug. 5.

Gossip Girl star Leighton Meester joined her boyfriend, Sebastian Stan for a daytime "brunch-fest" at Day & Night Restaurant Beach Club in Southampton where they sipped from several bottles of Bertaud Belieu Rose Champagne with a group friends in a private poolside cabana, including Mischa Barton's co-stars on The Beautiful Life, Sara Paxton, Nico Tortorella and Ben Hollingsworth. Leighton and Sebastian were in the Hamptons for the weekend, for the East Hampton premiere of his film Spread, starring Ashton Kutcher, later that evening.

The Secret Life of the American Teenager's Francia Raisa celebrating her 21st birthday at Blush Boutique Nightclub inside Wynn Las Vegas.

Real Housewives' Alex McCord and Ramona Singer drinking elit by Stolichnaya cocktails at Bridgehampton Polo.

Jermaine Jackson buying cupcakes at Crumbs in Calabasas,Calif.

Gossip Girl hottie Chace Crawford discussing work over dinner at STK in L.A. Chace, dressed neatly in a black polo shirt and jeans, enjoyed a bottle of Pinot Grigio which he paired with a 6 oz steak and mac and cheese. An observer said that Crawford seemed like such a nice guy, very polite and charming!

Newly brunette Samaire Armstrong at the Gavert Atelier Salon in Beverly Hills chatting about her new pilot for HBO, How to make it in America.

Annalynne McCord telling OK! "a healthy love life" is the key to staying in shape while at the Vision Street Wear/Spin Magazine Malibu Beach Bash and treating her sisters to a spa day at Thibiant Beverly Hills.

Recently engaged Jaime Pressly at Post'age Denim At Fred Segal Launch party.

Jesse McCartney at SoBe Lifewater Summer Fridays at Stephen Weiss Studios in NYC.

Jeff Beacher's touring variety act, Beacher's Madhouse, whose celebrity fans include Britney Spears, Jessica Simpson, Paris and Nicky Hilton, Quentin Tarantino, Lindsay Lohan, John Stamos and Jon Bon Jovi, among others, performed at Republic in New Orleans on