How can I find out how much I will get back for income taxes

You prepare your tax return. Since the year isn't over you would have to estimate your income.

Most of the tax prep software packages allow you to do what If scenarios.

Turbotax.com is a good place to start. I estimated my 2008 taxes there. Some laws may change before you actually file, but you should get a good idea what might be heading your way come January.

TaxAct.com is also a good website for such purposes.