Kimberly Winston provides more example of how the notion that religious people are more giving than non-religious people is bullshit. "In season of giving, atheist groups’ charity rebuffed" gets into some of the technical reasons this idea of religious givings superiority is a myth but leaves out a few as well. She also doesn't bring up some of the underlying philosophical problems with the stereotype. At various times I have pointed out problems with the methodology sued by some of the studies that have been conducted in this area as well as the reasons different groups give to "charity".
I wrote about this type of thing back in August 2012, "Generosity: A Perennial and Misleading Question"