I've heard an interview on the planet money podcast some time ago where they had a teacher on. The teacher said, that she uses one dollar bills which she hands over to a student one bill at a time to give them a sense of larger numbers. She explains to them that it would take about 11 days to give them 1 million, but about 31 years to give them 1 billion. I thought this was a nifty way to 'visualize' these abstract numbers.