The big mover for economic data today is Gross Domestic Product, which (if you aren't familiar with it) is the sum of all private domestic consumption, plus gross private domestic investment, plus government spending, plus the current trade balance. It is pretty much assumed to represent the health of a nation's economy.
GDP reporting is, in a word, peculiar. It gets reported three times for each quarter. There is an advance report, a preliminary revision the following month, and then a final revision. This month, we're getting the preliminary revision for Q4 2010. The advance report showed GDP up 3.2% for the quarter, with the price index (one possible measure of inflation) up 0.3%. The Econoday-surveyed analysts are looking for the preliminary revision to show Q4 GDP increase to 3.4%, with the price index remaining at 0.3%.
For the actual results we turn to the Bureau of Economic Analysis, which has chosen to crush the fragile hopes and dreams of the analysts. In the preliminary revision, real GDP was revised downward to 2.8% for Q4 2010. This still represents an increase from Q3's 2.6% final result, but it is not calculated to make the markets happy. The price index rose 2.1% in Q4, unchanged from the advance report, while the "core" price index rose 1.2%.
I would say that this is likely to shake the markets up, but the futures are still green. As of right now, anyway. Go figure.
 I took the 0.3% price index for Q3 from the Econoday page. I'm not sure where they got it from, looking at the BEA information.