Of course you can. Minecraft has a folder with worlds in it in Application Support, so just put the map in.
Try using a map editor, like MCEdit.
In beta 1.6.6, you can just get the map by making a compass, put it in the middle of the 3x3 crafting box, then surrounding it with paper.
Put the new map in the minecraft_server folder then open the server.properties file and add the name or number of the map next to level-name=.
Some might, but an adventure map is a MAP, not a mod. Just search for "adventure map" on Google or the Minecraft Forum.
Just Yahoo/Google "Minecraft maps", go to the minecraft forums or go to Youtube and look at some of the videos. They some times put a link to the map in the description of the video for you to download.
It can be used for adventure map building to put it in chests. Other than that, it's pointless.
Either go into the single player menu in Minecraft and select which one you want or add the map/world into your "saves" folder. If you want to add maps to your Multiplayer then just put the map into the folder your server app is in then add the name of the map into the "server.properties" folder for the game to see it.
Go to the minecraft folder in your files, press saves, and drag the map into the saves folder.
no because that's a map and you need Minecraft to install it in your Mincraft
You can make a custom map on minecraft with out a map editor by building or demolishing certain land features or you can use a seed by typing your seed in the bottom box on the "create new world" menu.
There is lots of them.