The New York Times has a set of graphs on the cost of the wall street bailout so far, both in dollars spent and in pledged.  So far, $1363 billion dollars has been spent.  $7.8 trillion, i.e. $7800 billion, has been pledged. 

To give you an idea as to how much that is, the US debt is over $10.6 trillion and total US government spending in 2007 was about $2.7 trillion.

Thanks to The Big Picture for the link to the NYTimes.