I am far from a tax expert.
But this is what I would guess since no one else has tried. I'd like to know the real answer since I never do my taxes. I let Turbo taxes do the calculations.
You will have to pay in social security and medicare. There goes 6.2% and 1.45% repectively.
So $15000 x .0765 = $1147.50 goes toward SS and Medicare.
I did a quick search for 2007 income tax brackets and got this. Now I don't know if you are taxed on total on your total earnings or total earnings less ss and medicare.
http://www.irs.gov/formspubs/article/0,,id=164272,00.html
Anyway you will be taxed another $782.50 for the first part and then be at the 15% rate after that.
So assuming you are taxed on your total amount (not after ss and medicare are taken out, you will be taxed another (15000 - 7850) x .15% = $1072.50
So my guess is your total take home will be
$15000 - 1147.50 - 782.50 - 1072.50 = 11997.50