Punch up: www.interest.com

Why it clicks: The power of compound interest is easier to understand when the numbers are in front of you. The concept is simple - earning interest on interest that you've already accrued - but the impact can be tough to visualize. Most compounding-interest calculators will tell you how much your money will grow after a certain number of years. The calculator at Interest.com lets you add to the kitty and compute the final amount. Look on the mortgage calculator page under the deposit calculator heading.

The download: Just input the numbers and you'll get a total amount and an annual breakdown. Say you want to start putting away $40 a month for the next 10 years. You'll have $5,308.78, assuming a 2 percent rate of return. Not too shabby for missing a couple of Starbucks a week.

- Lorene Yue, Your Money