Otomata, at EarSlap.com, is a fun, little Flash toy that allows you to create music by inserting living cells into a grid that then follow rules to generate a sequence of music. Since the rules allow the cells to interactive, you can create a random, evolving musical sound. It can make for quite a bit of fun and pleasant sounds.
Each alive cell has 4 states: Up, right, down, left. at each cycle, the cells move themselves in the direction of their internal states. If any cell encounters a wall, it triggers a pitched sound whose frequency is determined by the xy position of collision, and the cell reverses its direction. If a cell encounters another cell on its way, it turns itself clockwise.
This set of rules produces chaotic results in some settings, therefore you can end up with never repeating, gradually evolving sequences. Go add some cells, change their orientation by clicking on them, and press play, experiment, have fun.
You can see a demo here:
But better yet, go try it from a Flash-enabled browser and see (hear) for yourself.