Guests like Rosario Dawson, Sean Penn and Ali Hewson gathered at the Project7ten green home in Venice to drink Acacia cocktails and celebrate the second edition of Edun and One's ONE T-shirt campaign. Hostess Helena Christensen, who photographed celebrities in the shirt—proceeds from the sale of which will help fight AIDS—eyed her work while Josh Hartnett spent most of his time outside the house on the patio. "I was so excited when the One campaign first came out," said Dawson. "I went online and joined right away."

—With reporting by Elizabeth Jenkins, Kwala Mandel, Jennifer Muirhead and Lindzi Scharf