How much tax will I have to pay for 2009 if I did not take my federal witholding out of my unemp checks weekly?

It depends on your total income, as well as things like your filing status, dependents if any, and deductions. If you get a job for the rest of the year you might be wise to put zero allowances on your W-4 to make up for it. If $25 a week was taken out for part of the time, there's some chance you could get a refund, but not real likely unless you have more taken out this year.

For a rough estimate of what you will owe if you do not find a job, take the total unemployment compensation for the year, add any other taxable income, subtract your deductions and exemptions, multiply by 10-15%, and subtract the amount that was withheld. (If the result is negative, then you may receive a refund.) If you do find a job, then the amount owed or the amount of the refund depends on how much you make at that job and how much is withheld at that job.