Koch Snowflake (animated)
This is one of the earliest described fractals, and it's based on an equilateral triangle. After a few iterations, the triangle turns into a beautiful, self-similar flake.
See the animated version here
Circles (animated)
A simple fractal based on dots in a square pattern.
See the animated version here
Spiral 1
A variation of a spiral fractal.
See it rendered here
Spiral 2
A variation of a spiral fractal.
See it rendered here
Spiral 3
A variation of a spiral fractal.
See it rendered here
Tree
A simple tree fractal.
See it rendered here
Develop your own!
If you are interested, you can download a package containing all fractals
here. Each is based on two JavaScript files: fractal.js which is a library in charge of calling a delegate, as well as rendering progressively, so that the generation is animated. The second JavaScript file is particular to each fractal, and defines a delegate generator function, along with the initialization of the fractal library.