Prerequisites

1) Make sure you have marmelade repo enabled in your ~/.emacs.d/init.el

(setq package-archives '(("marmalade" . "http://marmalade-repo.org/packages/")))
(package-initialize)

Steps

1) M-x package-install pbcopy

2) Add this code to your ~/.emacs.d/init.el

(turn-on-pbcopy)

3) M-x eval-buffer # reload your init.el

Result

Now everything you copy from Emacs will also be in the OS X clipboard and vice versa

Cheers

Daniel Nelson for the pbcopy package