Medical Savings Account (MSA) Calculator
I am amazed more people do not use these plans. Their are also similar Child Care "Flex" Savings Accounts to cover child care costs. The general idea is you contribute some fixed pre-taxed amount of money each year, and you either submit receipts and are reimbursed for all eligible expenses, or you use a debit card to directly pay for eleigble expenses. So you are in essence getting your own money back, just that it has never been taxed. Note that not only are these funds exempt from federal and state tax, but also from the 7.65% FICA tax as well.
Also note that these work as zero interest loans on top of all the tax savings. For example, if it is December and you want to have Lasik surgery in January, you add $1800 to your MSA account for the next year and get the surgery done in January. The MSA account deducts an extra $150 every month from your paycheck throughout the year, but you have already received the surgery without having paid all that money yet.