Fractal Maker WARNING: can be addictive!
The following images are from Wikipedia, and have been released into public domain or under the license agreement stated.
Koch Snowflake:
Sierpinski Triangle: licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
Attribution: Dino at en.wikipedia
Sierpinski Carpet (click on carpet to see the progress)
Mandelbrot set:
http://en.wikipedia.org/wiki/Mandelbrot_set
Image of the Mandelbrot set with continuous coloring: created by Wolfgang Beyer with the program Ultra Fractal 3 and is free to be shown here under Creative Commons Attribution-Share Alike 3.0 Unported license
Zooming in on the Mandelbrot Set: (click on the picture to start)