All my batting scraps get cut up or pieced to make a lap quilt.
I do a lot of quilt-as-you-go and Reversible Quilts (see Sharon Pederson) and use tons of 13 or 7 inch blocks. Anything smaller gets sewn together until the piece is large enough for a lap quilt. I only make one wall hanging a year, I think, so would otherwise never use up the mounds of batting that accumulate.
I didn't originate the idea, but it does keep my leftover batting from ovewhelming me!
BTW, by doing this all at once, I discovered that the original Soft and Crafty ultraloft (for tying quilts) had been cheapened. The original stuff WAS 3/4 inch thick while the current stuff never measures even 1/2 inch. Really irritating.