You can work from when you're 14 in Australia (possibly with parental consent, I can't remember, I was 14); but there's fun issues with contracts and international companies, I'd assume.

From Western New York, when I was 15/16 I got a workers permit to allow me to work at a pizza shop (Mark's Pizzeria) but it had a lot of restrictions like limited hours on a school night. This was over 15 years ago so I am not sure what the laws are now.