Try $4.28 trillion dollars. That's $4,284,500,000,000 and more than what was spent on WW II, if adjusted for inflation, based on our computations from a variety of estimates and sources*.
Not only is it a astronomical amount of money, its' a complicated cocktail of budgeted dollars, actual spending, guarantees, loans, swaps and other market mechanisms by the Federal Reserve, the Treasury and other offices of government taken over roughly the last year, based on government data and new releases. Strictly speaking, not every cent is directed a result of what's called the financial crisis, but it arguably related to it.
Some 68-percent of the sum falls under the Federal Reserve's umbrella, while another 16 percent is the under the Treasury Asset Relief Program, TARP, as defined under the Emergency Economic Stabilization Act, signed into law in early October. (The TARP alone is bigger than virtually any other US government endeavor dating back to the Louisiana Purchase. See slideshow.)