Colbie Caillat put "Bubbly" on MySpace last September and by early this year had shot up to the site's No. 1 unsigned artist spot, a position she maintained for four months. Universal Republic jumped onboard during that run and stuck with the charming track as the first single from a July LP. Something of a female Jack Johnson, Caillat's warm vocals along with a gentle acoustic arrangement effortlessly conjure the idyllic California she calls home. Gaining quick acceptance at triple-A, this sweet-without-being-soppy tale of the first blush of new love is sure to enchant hot AC next. —Susan Visakowitz