Here is what we do...even when we were broke and barely putting food on the table. The kids, like the adults, in our family get a small sum of disposable income to do with what they want. For my children it has been as little as $0.10 per week per child, especially when we had very little. I started this from day one. We then require them to give 20% to charity...we do this in the form of a piggy bank that we then donate when it is full. We also then require them to save 20% in a savings account...which we also use piggy banks for until they have $5 or more them and make sense to deposit. The rest they just keep in their rooms and spend as they wish. They do this with all their money including birthday gifts, amount they earn from doing special projects or chores that are above and beyond their normal household responsibilities. It has worked so well that between the 3 of them, they started saving money last June and saved enough by December of their after savings and after charity money to go in together to purchase a TV, a Game Cube, a bunch of games and extra controllers for their playroom as DH and I told them we wouldn't buy them, but they could if they saved up enough...ROFL never thought they would do it...it was a sad trip to Best Buy for us that day.

That is one of those "never promise something you aren't willing to follow through with" lessons of parenting.
It is very simple to teach these lessons...they have learned the lesson of just because you have money doesn't mean you spend it(their disposable income just sitting in their rooms waiting to be spent), saving for a rainy day is a great thing(their savings account), and giving to charity(or taxes as you are older). But, I was not raised with learning about money, my parents never gave me any and I was required to earn money by doing chores rather than being given an allotment for being part of a family. So, for me it is very important they grow up with these lessons just being a "part of life" like healthy eating, good dental hygeine, bathing regularly, etc.