This is a really cool program.  You can get it here:
http://www.apophysis.org/
The latest beta version is 2.05 beta 2.  You're creating amazing images using algorithm formulas.  
 http://www.renwebdesign.com/fractals/index2.html
 Anyway, it's a lot of fun and once you experiment with it, you'll be able to create some pretty cool images!  :D 
Here's one of mine:
http://img264.imageshack.us/img264/5400/apophysismonrb7.png

Have Fun!! :D 

You may also want to try Ultra Fractal 4:
http://www.ultrafractal.com/