DS has a "youth saver" account that rewards with a high rate of interest each quarter if you make at least one deposit of any amount and no withdrawals in a month. We opened it pretty much when he was born and $20 a fortnight gets debited automatically from our account into his. Plus all our loose change/coins go into his money box and when it's full goes into his account. His grandparents deposit some pocket money into it as well.

Doesn't seem like a lot but it will all add up to a nice amount by the time we're ready to give it to him (maybe when he's 30!)