I've been meaning to write one of these for ages, and now I've done it. It's a Swing program to illustrate the different possible games that you can get by tweaking the parameters of Conway's Game of Life. See the link for an explanation.
Alternatively, play with the sliders and buttons and watch the bizarre patterns emerge.
Hint: If it looks like nothing's happening at first, try hitting the 'New Seed' button a few times to get the thing going.