Software

Electric Sheep Screen-saver - Electric Sheep realizes the collective dream of sleeping computers from all over the internet. Free; Linux, MacOS X.
http://electricsheep.org/

Physis - Physis is a software platform for testing the evolvability of different assembly-like programming languages.
http://physis.sourceforge.net

Artificial Life by Jpr - Introduction to artificial life. Each chapter is illustrated by a program or an applet. Chapters are available in PDF.
http://www.rennard.org/alife

Darwinbots - A free artificial life program running under Windows. Similar to C-Robots with a biological bent, where the robots mutate and evolve over time.
http://www.darwinbots.com/WikiManual/index.php?title=Main_Page

Java Fish - An aquarium simulation written in Java. The program uses neural networks for all of the fish being simulated, and the fish are artificially evolved from random starting information.
http://sourceforge.net/projects/jfish/

Life Simulation Game - An artificial world of lifeforms which eat, move and reproduce. Each species is controlled by a program, and you can write your own lifeforms.
http://www.geocities.com/peterstephenbailey/

BugBots - BugBots is a game, sort of. Really it's a project in Artificial Intelligence, and Object Oriented Design with heavy abstraction.
http://bugbots.sourceforge.net/

Kasprzyk's ALife Page - Artificial Life for the Macintosh.
http://www.kasprzyk.demon.co.uk/www/alife/

Archis Evolutionary System Simulator - An artificial life simulator project that can also function as a genetic programming system. Written in Java with a graphical interface.
http://www.greythumb.org/people/api/archis/

Applets for Neural Network and Artificial Life - A list of programs using alife type techniques (English/Japanese).
http://staff.aist.go.jp/utsugi-a/Lab/Links.html

Flocking Experiment - Two flocks of birds migrating to different locations flock together before splitting apart.
http://www.oursland.net/projects/lakeflock/

The Breve Simulation Environment - MacOSX software for simulation of artificial life and decentralized systems.
http://www.spiderland.org/breve

PS-I - A sourceforge project for an environment for creating and running agent-based models. Tcl/Tk scriptable, cross-platform (Windows and Linux/Unix).
http://ps-i.sourceforge.net/

Artificial Life on the Web - A web-oriented artificial-life site: Alife, genetic-algorithm and cellular-automata experiments written in cross-platform web languages (Java, tcl/tk), with free source code.
http://www.aridolan.com

Manna Mouse - Exploration of fitness landscapes.
http://www.caplet.com/MannaMouse.html

Chaco the Chaos Collection - A collection of small tools for Chaos Modelling, based on ideas of Life game, Tierra and others.
http://sourceforge.net/projects/chaco/