Context Free is program for generating recursive structures, based on Chris Coyne's CFDF grammer. It's easy to use, open source, and outputs very clear images. Within minutes, I was able to produce the image on the right.
Recursion is handled particularly well. The image is rendered iteratively, allowing it to grow without slowing the computer down. Rendering continues until it gets down to features that would be too small to see. Very nice!
It's probably time to a new generation of software toys for playing with chaos and generative graphics; the classic applications are all from the nineties. With an emphasis on usability, and integration with the web, these toys could be accessible to everyone.