Fractals are commonly used in computer graphics to generate terrain. On natural way to proceed is start with a tetrahedron and then determine the mid-point of each edge:

Each mid-point is then displaced by a "randomly selected" value and the tetrahedron is subdivided. For example:

This process then continues until the desired mesh is obtained.

Image (A Collection of Terrains)
Image (Another Collection of Terrains)
Video (640x480, WMV, 6Mb)
Video (640x480, AVI, 14Mb)
Video (320x240, MPG, 4Mb)