The first memory I have of teaching Boo money was with a simple game using spare change. You hold up the coin if the child can tell you the name they ‘win it’. Once the names are clear you move to the name and its value. Once the game gets too expensive you stop playing it.
Unit Money/Economics (for a child already comfortable with the basic values & names of currency, adding & subtracting basic amounts using coins, & shows an interest in deeper understanding of what money is including the historical 'hows' and 'whys'.)
Mint (via the net) US