One of Ember's favourite books from the library is 'Miranda's Numbers'. It's written by Miranda Harcourt and someone else, and uses lots of different techniques to subliminally implant numbers into children's brains. That sounds more sinister than it actually is, and it's a nice enough story.
Anyway, it starts from "0 - zero looks like an empty plate" and I happened to be explaining the concept of zero to Ember at a time when she was eating a carrot. Consequently, when we were reading the book at bedtime last night (sans carrots), when we got to this page, Ember held up her fist and said "Look mummy, zero, got no carrots!"
I have visions of her getting to school aged five, and a teacher saying "How many do I have, if I have zero?" and Ember replying "You got no carrots!"
Ah well, it's a start :)