I have built a simple calculator for Federal (USA) income tax for year 2010 per both current law and Jan Schakowsky's proposal to add new tax brackets at the top end and charge a higher marginal tax rate for income that reaches those new brackets. This calculator assumes a married couple filing jointly, neither person blind or having other exceptional circumstances that affect tax rates or the standard deduction, and assuming in fact the couple declares the standard deduction rather than itemizing deductions.

How I got the data&algorithms to use in this calculator:
For learning the amount of the standard deduction, I started at this starting page on the IRS Web site, and then answered all the questions per the above assumptions, whereupon I arrived at this final page, where it shows the standard deduction as $11,400.
For learning the tax brackets and corresponding tax rates, I consulted the WikiPedia page.
For learning the additional higher tax brackets proposed by Jan Schakowsky in her "Fairness in Taxation Act", I consulted this article in the Huffington Post.

Link to my calculator here.
Note: The tax brackets and rates are the same for 2011 as for 2010, but the IRS standard-deduction page doesn't have the year 2011 as an option, so I had to use 2010 instead.

See also my first draft of proposed increased tax rates on highest brackets beyond what Jan proposed: here