I'm hoping that you're thinking of a
realtime display, in which the
peaks roll off to create a true waterfall effect.
Baudline (
http://www.baudline.com) is a fantastic viewer that does fft
cascade. I've used it for a couple of years, and it is great for figuring out
how different sounds "work", and it has an oscilloscope-type display as well.
Cheers,
Jason Downer