Prepaying your mortgage can be a great way to save a bundle of extra cash over time. Doing so not only saves in interest cost but builds equity faster and also shortens the term of your loan, so you'll own your home free and clear much sooner.
HSH's free, downloadable Homebuyer's Calculator Suite allows for regular or irregular prepayments of principal, and will show you the effect your extra effort will have on your total loan costs and term.