Parallax mapping is a small modification to bump mapping that tries to take into account the height of the surface. Here are today's results. I went with a different texture today, one with more pronounced grooves to better demonstrate the effect.
Texture:
Normals:
Height:
Bump mapping:
Parallax mapping:
You can see in the parallax mapped picture that the grooves between the stones are obscured (or partially obscured) at small angles.