Day Z is played on Arma 2's main map, Chernarus. It's a 225 km² foresty facsimile of the Czech Republic, and it's easy to get lost in (literally and figuratively). You don't spawn with a map or a compass, so you're left to use landmarks and road signs to orient yourself.
There's already a handy virtual Day Z map online, but Bohemia has put a wall-worthy paper map of Chernarus up for sale. Also included are hard copies of Operation Arrowhead areas Sahrani, Takistan, Shapur and Proving Grounds and eight Arma 2 postcards. Click over here to buy a Chernarus map .
I've been using mine (Bohemia was handing them out at E3 2011) throughout my Day Z diary . It beats asking bandits for directions.