Reverse ball juggling is almost the same as the normal 3-ball cascade. The only difference is that instead of throwing the balls towards the middle of the balls falling, you throw the balls on the outside of the balls falling.
In the regular cascade, you catch each ball on the outside, and throw on the inside. With the reverse cascade, you catch each ball on the inside and throw on the outside. It sounds simple, until you try it out...
Watch this video. It gives you a better idea of what the trick looks like. It's not DVD quality, but it's the best I have right now. Watch it in your browser, or download it to a disk. I don't care what you do with it.