No, I'm not reanimating things in my basement. Yet.
One of the most recognized examples of cellular automata is Conway's Game of Life. With a few simple rules, it simulates a population that evolves over time, sometimes producing self-replicating patterns. The versions I've found on the Web have the classic rules:
1) if a living cell has only one living neighbor, it dies.
2) if a living cell has more than four living neighbors, it dies.
3) if an empty cell has exactly three living neighbors, it comes to life.
What I'm looking for is a program, website, bit of coding, etc. that allows me to tinker with the rules so that I can find a way to simulate a gradual spread without a death factor, or with a higher death threshold, so that the result isn't too dense or too attenuated (possibly even including some random probability factor to make things interesting.)