Summertime is in the air and celebs are getting into the groove, wearing the latest warm weather fashions.  Reese Witherspoon shopped until she dropped at Barneys New York in Beverly Hills, showing off her superior style sense wearing a bright, geometrically patterned mini with Christian Louboutin wedges, a quilted Lanvin bag and a fab fedora.  Amy Winehouse, on the other hand, had a bit of a slip-up!

PHOTOS: Cameron Diaz, Tom Cruise, Claire Danes, Hugh Dancy, Reese Witherspoon, Ryan Kwanten, Leighton Meester, Kendra Wilkinson, Amy Winehouse, Serena Williams, Claudia Schiffer, Orlando Bloom, Kendra Wilkinson, Queen Elizabeth, Beyonce, Jennifer Garner, Helen Mirren, Nikki Reed And Teresa Palmer In The Best And Worst

The surgically enhanced singer showed off a bit too much of her assets in a lowcut bustier top, shoving a pack of cigs into the skimpy top to make matters worse.  With a bandana tied around her head and acid-washed skinny jeans added to the mix, the bad girl was in desperate need of wardrobe Rehab!

PHOTOS: More Best And Worst

Cameron Diaz was in sizzling style in Brazil, scoring herself two Best looks.  At the premiere of Knight and Day in Rio, the sexy starlet rocked a dangerously high-slit green satin mini, changing into a geometric print Givenchy blouse for a chopper ride later in the day. Beyonce jazzed up a jumpsuit with covetable Fendi Cinderella Lucite-platformed heels, while
Leighton Meester showed off a little too much of her black bra under a Proenza Schouler tie-dye tank.

What Girl Next Door made our list twice, scoring a Best and Worst look, while promoting her new book? Check out the gallery in Style to find out.