The auto update for GRAW 2 has added a section to the main menu entitled "Exclusive Map". After linking your Xbox Live account to your Ubisoft account in this menu, you can download the Nowhere map for free. By linking your account you also gain access to an exclusive section where you can download an exclusive Mega 64 video and Penny Arcade wallpaper.
For more info and links to register go to http://ghostrecon.us.ubi.com/ and follow the instructions