www.geom.uiuc.edu/software/tilings/Tessellationresources. Lists programs for various platforms that allow the user to create designs featuring the rosette, strip, and wallpaper patterns.

escher.epfl.ch/escher/ Interactive Escher Web Sketch program that allows a user to design repeating patterns. Choose a wallpaper pattern using crystallographic notation and draw on the screen a colored design for the motif; the program then reproduces the motif using the pattern. The software (for Windows, Macintosh, and Unix) can also be downloaded.

www.geom.uiuc.edu/java/Kali/ Interactive Java Kali Web program that lets the user draw pictures under the action of rosette, strip, or wallpaper groups. Versions for various platforms can be downloaded.

www.wordsmith.org/~anu/java/spirograph.html Interactive Spirograph Java application (which you can download) that lets you do electronically what the Spirograph toy does.

csdt.rpi.edu/african/African_Fractals/ An African fractals site.

classes.yale.edu/fractals/index.html Website for Benoit Mandelbrot’s course in fractals at Yale. Features many applets for different kinds of IFS (e.g., incorporating randomness), including a fractal music composer.

www.math.smith.edu/phyllo//index.html Phyllotaxis: An interactive site for the study of plant pattern formation, created by Pau Atela and Christophe Golë.

www.maths.surrey.ac.uk/hosted-sites/R.Knott/ Fibonacci/fib.html Fibonacci numbers and the golden section. Splendidly illustrated extensive web pages by Ron Knott about Fibonacci numbers and the golden ratio: their occurrences in nature, their applications, puzzles, and much more.

fractalfoundation.org/OFC/OFC-index.htm Fractal Foundation online course. Amazing photographs of fractals in nature, applications of fractals, and artwork of fractals of all kinds.