If You Like Ann Brashares'
The Sisterhood of the Traveling Pants Series,
Try These...

Teen Fiction
Bauer, Joan.  Hope Was Here.
Bauer, Joan.  Rules of the Road.
Brian, Kate.  The Princess and the Pauper.
Chambers, Veronica.  Quinceañera Means Sweet 15.
Creech, Sharon.  Bloomability.
Dessen, Sarah.  Keeping the Moon.
Devillers, Julia.  How My Private Journal Became a Bestseller.
Guarente, G. P.  Hook, Line, and Sinker.
Hantman, Clea.  Goddesses series.
Hopkins, Cathy.  Mates, Dates, and other Cosmic Kisses.
Kindl, Patrice.  Owl in Love.
Naylor, Phyllis Reynolds.  The Alice series.
Perkins, Lynne Rae.  All Alone in the Universe.
Rennison, Louise.  Angus, Thongs, and Full-Frontal Snogging.
Ruston, Rosie.  Just Don't Make a Scene, Mum!
Sheldon, Dyan.  Confessions of a Teenage Drama Queen.
Sones, Sonja.  What My Mother Doesn't Know.
Tashjian, Janet.  Tru Confessions.
Van Draanan, Wendelin.  Flipped.