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
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/
Avida - An auto-adaptive genetic system designed primarily for use as a platform in Digital or Artificial Life research. Download source, binaries and documentation. Unix/Windows. - http://dllab.caltech.edu/avida/
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/
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/
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/
Kasprzyk's ALife Page - Artificial Life for the Macintosh. - http://www.kasprzyk.demon.co.uk/www/ALHome.html
The Breve Simulation Environment - MacOSX software for simulation of artificial life and decentralized systems. - http://www.spiderland.org/breve
Physis - Physis is a software platform for testing the evolvability of different assembly-like programming languages. - http://physis.sourceforge.net
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/
Flocking Experiment - Two flocks of birds migrating to different locations flock together before splitting apart. - http://www.oursland.net/projects/lakeflock/
Manna Mouse - Exploration of fitness landscapes. - http://www.caplet.com/MannaMouse.html
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