[parttimepro]

Well, think about it this way. If you have unpaid credit card debt, you're paying about 20% per year on that money. You don't get any kind of tax deduction either, like you would with a mortgage. So paying off that debt is like finding an investment that pays a guaranteed 20%/year, tax free. Professional investors would wet their pants if they could get a guaranteed 20%.

If you're talking about a mortgage or student loans, you may want to diversify. Student loans in particular are generally subsidized, meaning you're paying below market rates for the debt. If you've locked in a low interest rate, it may be worthwhile to put some money into investments rather than prepay those debts.