This free app from the makers of TurboTax can help you estimate how much you will owe in federal taxes this year. The app, which is available for the iPhone, iPad and Android phones, uses TurboTax's patented step-by-step walkthrough to figure out how much money you made during the tax year and how many deductions and credits you can claim.
Questions are straightforward; most of the answers can be found on your paystub, your W-2 form, or off the top of your head ("How many children do I have again?"). Your tax status is displayed with a continuously updated gauge that swings from red (you owe money) to green (you're getting a refund) as you answer more questions [source: Cabebe].
While the calculations aren't official -- don't make a down payment on that hot air balloon just yet -- it's a fun and simple way to get a tax day preview.