Brownian, a freely redistributable program by:
John M. Olsen, 1547 Jamestown Drive, Salt Lake City, UT  84121-2051

Brownian is loosely based on both fractal theory and brownian motion.

A conventional way to use this technique is to start with a flat plane, 
then pick a line on it and raise everything on one side, and lower
everything on the other side.  This is repeated until you have what looks
like a patch of a fractal mountainside.

These fractals can be tailored to match a specific general design by putting
constraints on where the lines are to appear.  To get a mountain range, you
just need all the lines to point approximately the same direction.

My approach was tailored to the Amiga by my using triangles instead of 
fault lines.  I alternate between raising and lowering the color values 
within a random triangular area, then toss in color cycling just for fun.
I directly use the blitter to do plane by plane addition to modify the
color values within the triangle.

The program is run by either selecting the brownian icon, or by typing
"brownian" at the CLI prompt with no parameters.