How can I copy part of a Minecraft world into another Minecraft world?

Backstory

The places that have been built on in my world aren't that big. It's a ~100x~100 square, a ~150x~50 rectangle in the Nether, and another ~100x~100 square accessed by portals.

The world is currently unplayable due to the server console spending so much time printing errors that the players time out. That, and for some reason it decided to spawn hundreds of sheep.

So I was wondering, is it was possible, and if so how, to move sections of this world into another, new, world?

Solution 1:

Yes. Use MCEdit. You can copy the section in your old map, and save it as a schematic, which you can then import and place into a new world (generated with Minecraft by starting a new game), overwriting what was there before. Make sure Minecraft is closed while you are using MCEdit, otherwise you can corrupt your map.