Software

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

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/

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

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

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

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/

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/

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

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/

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

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/

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

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/

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

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

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/