I only use Warm & Natural. (right now, Joanns has it on sale with free shipping)
I've also used old (washed very well) blankets too.
I've used wool in the past, but have found that the quilts have shrunk because many people don't pay attention to the washing instructions.
Baby quilts, at least the ones I make and give away, get washed ALOT, so it would need fabric/batting that will not shrink alot.