06/13/2011 at 02:00 PM EDT
was in Chicago for the B96 Summer Bash – but the singer made time for the club scene. Jonas partied with DJ Syphe at club The Underground, where he debuted his new dance song,
"See No More," to a packed house. Days before trekking to the Windy City, Jonas stepped out for a cheeseburger dinner at West Hollywood's Chateau Marmont
. He was in good spirits as he drank a soda and enjoyed his meal with two guy friends, according to an onlooker.
In the Big Apple, Fergie
celebrated the two-year anniversary of nightclub Avenue
along with her Black Eyed Peas bandmates. The group did a deejay set and took over two tables. Fergie also performed several songs and waved to Nicky Hilton
before heading out with the socialite. Next stop? The ladies dropped by nearby Artichoke Basille's Pizza & Bar for some late-night grub.
's Alexander Skarsgard
arrived at Equinox
in West Hollywood very focused and serious about his workout. The actor sported sunglasses, two pairs of black shorts (bike shorts and regular) and a blue T-shirt, then hit the elliptical machine for some cardio.
left his wife and son
at home for a night out at the Chateau Marmont
. After greeting friends on the patio, the Brit made his way to his own table in the corner and kept a low profile. Still, Bloom was laughing a lot with his friends. Says an onlooker: "The mood of the whole table was very jovial, and Bloom seemed to enjoy his night."
By KRISTIN BOEHM, JENNIFER GARCIA and JESSICA WEDEMEYER