With the new world generator in minecraft, you can type in seeds, which change the look of the generated worlds. I type random words and see what happens. Post good seeds here.
404 - A desert with a big gravel patch. hitting the patch reveals a cave that goes down to bedrock, full of lava, redstone, and diamonds galore.
snake - Makes a snowy, hilly world with steep caves that go to bedrock
flatlands - makes a relatively flat map
Post some of your own seeds!