Bankrate.com provides a good loan amortization calculator you can use whether you are making payments on a loan, or someone else is making payments to you. This calculator goes farther than many loan calculators by showing the interest, principal amount, and principal balance for the each year, for the entire length of the loan.
Loan amortization calculator: http://www.bankrate.com/brm/amortization-calculator.asp
amortization-calculator[1].asp (49.56 KB)