This technique may not be directly useful, but following the tutorial will brush up your Cycles skills :)
In this short tutorial, we'll be creating FAKE (but fancy looking) reflections ob any object and surface in Blender (Cycles Render). You'll be able to have certain parts of the surface reflect different colors.
So why should we need to know this trick? Well, you don't.. This trick doesn't actually make your scenes look any more realistic. But then again, depending on how you use it, it can create some jaw-dropping scenes. For example, you can use this trick to create huge water puddles that reflect a different sky or scene, or it can be used to get nice diverse reflections of a metallic model, or it can be used to get a slight colored reflection off of a street scene. This trick can be used for many things.
Another good benefit of this trick are, getting certain parts of your object to reflect different colors, without having to change the lighting or background.
Nothing that serious, but try it for yourself ;)