R.D.
Great book: Teeth are NOT for Biting.
Also, I used to pop (gently) my kids in the mouth BEFORE they bit, like as they were getting ready to (just like you'd tap a dog on his snout)... one time, my daughter bit me HARD when she was about a year old, didn't even see it coming... not my proudest mommy moment, but I bit her back. Not very hard, but hard enough to get the point across: IT HURTS! She never did it again.