My children (ages 8, 6, and 4 year old twins) have "Marble Jars".  They earn
marbles for good grades, doing chores etc.  They loose marbles for bad behavior
such as fighting with each other.  Every two weeks is "Pay Day".  They receive .25
cents for each marble.  They can spend their money any way they wish, but of course
they are encouraged to save their money.  This really encourages good behavior.

Stacy, Mom of 4
Cleburne, TX
Blue Rose Books and Gifts
http://www.bluerosebooksandgifts.com