That depends on your situation. Any government approved pre tax contributions such as 401 k if you are in civvies. Health care flexible spending account etc will simply move your money into another location for your use. New regulations now mean that contributions to health care spending accounts rollover. Post tax, retirement accounts such as IRAs save money for the future. Just keep in mind that this not only reduces your taxable income but locks that money into savings until the age of 65. You may be able to borrow against it depending on the institution.
Home ownership also defers a lot of your tax dollar. If you perform work from home in any capacity, you may be able to write off a portion of the mortgage itself as well as supporting utilities. Check with the IRS to be sure.
There are MANY ways to do this and a simple Google search will result in lists upon lists - from going green to home office deductions, childcare deductions, or medical expenses. It all depends on your personal situation.
