Here is a link to some really cool Java Calculators.

Mortgage Payoff-How much interest can you save by increasing your mortgage payment? This financial calculator helps you find out. Hit "Payment Schedule" to see a complete amortization payment schedule, and how much you can save on your mortgage! Compound Interest- How interest is calculated can greatly affect your savings. The more often interest is compounded, or added to your account, the more you earn. This calculator demostrates how compounding can affect your savings, and how interest on your interest really adds up!
Rent vs. Buy-Should you rent or should you buy your home? It takes more than looking at your mortgage payment to answer this question. This calculator helps you weed through the fees, taxes, and monthly payments to help you make a good financial decision. Be a Millionaire- What will it take to save one million dollars? This financial calculator helps you find out. Enter in your current savings plan and view graphically your financial results for each year until you retire! A complete report tells you when you will hit your Cool Million - and what you can do to reach this milestone on target!