Is there a way to make procedural materials like the ones here in Cycles for rocks, sand, landscapes, etc.?
Here's an image of what I'm trying to achieve:
I would say yes.
Here is an example I made in a few minutes entirely with material nodes:
Note that the color ramp near the bottom of the screenshot is going from
3 (to make the displacement stronger). To make colors darker or lighter than
0 you must type the values in directly.
This enables the Displacement settings in Properties > Object Data.