how about using a delay which has a short delay time and generous feedback but is also pitch shifted (and filtered)? Logic's Delay Designer does that pretty well and there are presets to start you up.. ?

Hard to say without actually seeing the balls! Innuendos aside, one sound I'm quite fond of is the sound of basketballs against different surfaces and locations, possible with the addition of a big piece of flapping plastic or something similar :-) To add some sweet sweet mass to it, a short-gated but full reverb on the bounce-sound (not the jiggle) might do the trick. I'd say you should look for the best possible sound to base it on before looking for effects! Don't use delay, sync each sound to each bounce instead. In nature, when bouncing without further influence, the repeats are based on the golden ratio, give or take on the first bounce depending on how hard you pressure the material, so a regular linear delay sounds unnatural, whereas a delay based on the golden ratio (think I have one in my Boss SE-50) would be depending on the animation being accurate. As I reckon it's probably a fabled story, that doesn't apply to the bouncing anyway, and will most definitely need to be individually synced :-)