I usually wake up at around 4.30 or 5.00am (but am in bed by 9pm), and I have to be out of bed by 5.30am to feed the cat! Better than any alarm clock.

The interesting thing is that, while I've had little success in imposing a consistent routine on my mornings in order to get more "this would be cool to do" stuff done, I am consistently, like clockwork, 30 minutes late for my day job! So clearly I have a routine, it just needs to be shifted back half an hour!