You think normal amortized loans are complicated? How about these bizarre Rule of 78 loans?. Here the amount of your interest paid each month is determined using a fixed linear scale, and the annualized interest rate actually changes each month. I could explain it all out, but I don't want anyone to fall asleep and drop their mouse on the floor! Just put in some numbers and find out for yourself.

UPDATE: - I was just notified that my annual interest rate calculation has been wrong for the past several years. Why didn't anybody else ever tell me? (Thanks, Steve!). In any case, now I instead print the annualized interest rate for each month as it slowly decreases over time. I have also removed the "Annual Interest Rate" option which was incorrect.