Accelerate your equity. Make bi-monthly payments instead of monthly. With bi-monthly plans, you make half a house payment every two weeks rather than a whole payment once a month. You'll build equity faster, save tens of thousands of dollars and pay off your mortgage years ahead of schedule. Talk to your mortgage lender and see if they allow this, but make sure they don't charge you a fee.
This is a simple way to save money that doesn't cost you any extra out of pocket money each month.