From della Q, here's Pippa Yarn Dispenser. The purpose of this bag is to protect your yarn so it's not rolling across the floor or so that your cat can't get into it.
If you like to walk and knit at the same time, the drawstring closures hang beautifully from your wrist. The bag is also a great way to feed your yarn so it won't get tangled. The bag has a flat bottom so it stands up and comfortably holds one or two skeins of yarn.