In a clear case of Notch putting the cart before the ography, he's announced on his blog that the 1.6 update for Minecraft will predominantly be made up of bugfixes, but will also add maps to the game.
It's a little bit cooler than it sounds. If another player picks up a map you've dropped, they'll be able to see your handiwork and add to it themselves. Notch also says there'll be a way to "clone" maps, so that two players will see one another as flashing marks on each of their copies of the map. Predictable song after the jump.