TUTORIAL AS QUOTED FROM SOURCE

love those nodes, here's a simple way to make a planetoid.

This tutorial assumes basic knowledge of a few things, like UV mapping and texture paint, however, if you would prefer, you can substitute a procedural texture for the UV texture, and forget about the geometry node. Also, if you do this, you will probably want the use the 'value' output of the texture node, instead of the 'color' output.

1) we are going to make a planetoid, so, to get started, make a sphere, and UV map it. Using texture paint, create a black and white image of where you want your continents to sit. you can make the water black and the land white, or the other way around, it really doesn't matter. Save the image, we will use it in a moment.
2) select your sphere, and open the materials window. Make a material for the land, with no specular, and a clouds texture for the bump map. Then, make another material for the water, with a high specular, and a stucci, or musgrave texture as the bump map. You can use the same channel, just choose add new, or toggle the appropriate channels on or off in the materials buttons. Anyway, we have two materials, one for land, one for water. make another material to hold the mask texture, or you can put it in one of the channels that's toggled off in your exsisting materials. Anyway, load the mask you just painted into a texture channel.
3) now, split your 3-D screen, and make a nodes window.
4) go back to materials, and on one of them, doesn't matter which, press the 'nodes' button, and you will see two nodes appear in the nodes window. The material will be solid black at this stage, so, in the nodes window, press the red arrow buttons, which will now be highlighted in red, and browse for a material. Choose the land material. Now, with shift+D, duplicate the land node, then, with the browse button, call up the water material. You now have two material nodes, and an output node.
5) we need three more nodes, a mix node, a texture node, and a geometry node. Call these up using shift+A.
6) use the browse button on the texture node to call up your mask texture, and
a) connect the 'UV' output on the geometry node, to the 'vector' input of the texture node.
b) connect the 'color' output of the texture node to the 'fac' input of the mix node.
c) connect the color output for the water node to either of the color inputs of the mix node.
d) connect the color output for the land node to the remaining color input of the mix node.
e) connect the color output of the mix node to the color input of the 'out' node.
7) render.