TheTreeTwiggies

Moxie and the Art of Rule Breaking has some geocaching too! An art heist+geocaching=

Oh- Book Scavenger by Jennifer Chambliss Bertman also has some mentions of geocaching. A large part of the book was inspired by geocaching as well.

The second book in the Candymakers series by Wendy Mass has some geocaching in it (the author herself is a cacher