It would be nice to see a weekly stat that showed how much money is collected in payroll taxes.
According to this site: http://www.shadowstats.com/article/an-analysis-of-withheld-income-employment-tax-receipts
The US Treasury publishes daily numbers showing the federal government’s daily cashflows.
The statement for July 7, 2011 is in pdf form here: https://www.fms.treas.gov/fmsweb/viewDTSFiles?dir=w&fname=11070700.pdf
It doesn’t strictly separate out withheld income taxes from FICA and FUTA taxes, but it does show in Table IV that the US Treasury received federal tax deposits (i.e., withheld income taxes and payroll taxes) of $7,164,000,000 on July 7th, has taken in $38,701,000,000 for the month of July so far, and has taken in a total of $1,354,968,000,000 ($1.3 Trillion, basically) for the current fiscal year.
The website I linked to above has some good discussion on what to be careful of when reading these daily releases.