In a similar vein as the previous post, Josh Bivens of the Economic Policy Institute has this:

Despite the overall contraction, the fingerprints of the American Recovery and Reinvestment Act could be seen in some aspect of today’s report. Federal government spending grew at an 11% rate in the quarter, adding roughly 0.8% to overall GDP. State and local government spending grew at a 2.4% annual rate, the fastest growth since the middle of 2007. It is clear that the large amount of state aid contained in the ARRA made this growth possible.

Furthermore, real (inflation-adjusted) disposable personal income rose by 3.2% in the quarter, after rising by only 1% in the previous quarter. A large contribution to this increase was made by the Making Work Pay tax credit passed in conjunction with the ARRA, as this was the first full quarter that the credit was in effect. Inflation-adjusted transfer payments (including a one-time payment to Social Security recipients)  rose at an annual rate of over 6% in the quarter as well. ...

The consensus of macroeconomic forecasters is that ARRA contributed roughly 3% to annualized growth rates in the second quarter. This means that absent its effects, economic performance would have resembled that of the previous three quarters, when the economy contracted at an average annual rate of 4.9%. In short, the recovery act turned this quarter’s economic performance from disastrous to merely bad. This is no small achievement, but with even more public relief and investments, the U.S. economy could do much better.

Crediting the stimulus with a three-percentage point increase in annualized GDP growth seems a little high to me, given that defense spending was up so much in the second quarter (and all those automatic stabilizers). But clearly the effect of the stimulus was significant.

--Noam Scheiber