I have discovered a wonderful handbook for learning some more advanced Processing: The Nature of Code. Although the book is specialized on cellular animation like graphics, it is full of useful tips for every kinds of Processing sketches.
Today I have studied the first chapter, about randomness and noises. Very, very useful. I have also done the suggested exercises quite simple, a part form the last one which is about a noise-driven 3D surface.
It took me almost one day to implement it, as I am not very comfortable with 3d programming, but in the end I made it.
Unfortunately it is not possible to embed Processing sketches into wordpress.com, but you can find the entire sketch here: http://www.openprocessing.org/sketch/84119
I will publish more while I keep studying the book. Promised!