Here is the book that I kept mentionning in the tutorial: The Nature of Code by Daniel Schiffman
The book explains many algorithm that attempt to reproduce natural systems (including swarms and fractals) using Processing, the java-based scripting interface.
You can download the book and make a donation or buy the hard copy. Try some examples, register to the Processing forum and to StackOverflow.com. Ask for help on the Processing IRC Channel.
For some example, you will need to need to download the Toxiclibs library and you might want to use the Eclipse IDE to speed up your workflow. You can also follow the great Plethora-Project.com tutorials by Jose Sanchez.