Celebs' Coolest Summer Jobs

Expanding her affordable-fashion empire, Jessica Simpson shows off her good jeans at the debut of Jeanswear, her new denim collection at her N.Y.C. showroom in June.

Jennifer Aniston mixes up her style scents for the London launch of her signature fragrance in July. "I want people to go, 'What is that? You smell great!'" the actress said of the eponymous scent.

Besides traveling on the Warped tour with her band The Pretty Reckless, Taylor Momsen fronts the ad campaign for Madonna's Material Girl fashion line. "Working with Madonna and Lola has been an unbelievable experience," the Gossip Girl star said of being styled by the music icon and her 13-year-old daughter.

Talk about a busy summer! Madonna takes on the role of director in July, getting behind the lens on the romantic drama W.E. in London.

Before teaching Chelsea Clinton to dance, DWTS pro Maksim Chmerkovskiy mans an ice cream truck, serving a cone to fellow dancer Tony Dovolani at an A/X Armani Exchange-sponsored event in L.A.

While most 16-year-olds spend their summer cramming for the SATs, Justin Bieber performs for thousands of fans during his first major headlining tour in Trenton, N.J. "Thank you to all the fans that came and SCREAMED!" he Tweeted. "I love u ladies."

He's baaaack! Summer's hottest leading man, Mad Men's dapper Jon Hamm, takes a water break during a sexy photo shoot in downtown Los Angeles in July.

Nick Jonas gets a standing ovation during his West End theater debut as Marius in Les Misérables – a play he starred in on Broadway as a kid. "What a night," he later Tweeted in June, "first show was amazing."

If a new baby and a TV show weren't enough, Kendra Wilkinson hawks copies of her bestselling book, Sliding into Home, which she signs for fans at a bookstore in New York City in July.

Speaking of reality TV moms: Bethenny Frankel beats the summer heat by whipping up SkinnyGirl margaritas – her new low-calorie beverage – during a cooking segment on The Early Show in New York in July.

Grammy-winning artist Wyclef Jean gets the political party started while greeting supporters in Port-au-Prince, Haiti, after announcing his intention to run for president of his native country in August.

Those hips don't lie, but they sure can shake! Shakira performs at summer's most-watched event, the closing ceremony of the 2010 World Cup in Johannesburg, South Africa, in July.

Dangerous curves ahead! Reality star Kim Kardashian makes a white-hot appearance as the official flag girl at the Amp Energy Bullrun Rally race, from New York to Las Vegas, in July.