What about the opportunity to make and save money in the military?
I'll go ahead and do that now before you ask for it:
2008 Military Pay Chart
If you have no rent, no grocery bills, no medical / dental bills, this is a lot of money. And for the record, these are basic pays, and do not include any bonus pays or combat pay or sea pay or anything other than basic pay. AGAIN, THIS IS JUST BASIC PAY.
Thrift Savings Plan
You can check out the Thrift Savings Plan too. It's basically a 401k that you are offeredthrough the military, and its something everyone is told about time and time again.
TreasuryDirect
If long term retirement isn't your thing, you can ignore the TSP and go with short term savings bonds. There's the link for them. And don't even try to say that people don't know about this stuff because you're offered these the very first day you get to boot camp.
At any point during this conversation, you can begin to respond to any of this with facts if you've like.