It's not possible to clone maps at the moment without cheating using the /give or /i command.
It's stated on the Minecraft Wiki that maps can only be cloned by using a command.
Below is a quote from Notch's Blog, he said that there will be some way to clone maps. He has not yet implemented a way to do so (wthout cheating).
You will also be able to (somehow) CLONE maps so that two separate map
items link to the same map data.
So in short, no at the moment you'll have to use the /i or /give command. Until Jeb makes a way to do so.