I have received lots of messages requesting for a tutorial on getting the "flat grass 1024x1024" map. So, here is the link to the download.
This save file is opened in a different way from what kiwiman has mentioned before. This one can be unzipped normally without The Unarchiver.
- Download the zip file.
- Locate the downloaded file and unzip it normally.
- Open a new Finder window.
- Navigate to User/Library/Application Support/minecraft/saves
- Drag the file into the "saves" folder
- Open the Minecraft Client and select the Flatland save.
Note: The Minecraft client will ask you to convert this save file. This is normal. Just click on the map and play the map, and it will convert automatically.
Here's a link to a site with some nice saves for downloading! Minecraft World Share
Leave your comments if you have any questions!