I just skimmed over:
http://rationaldreaming.com/2010/04/19/are-religious-people-more-charitable-than-non-believers/.
I will accept that religious people, on a whole, give at higher percents than secular individuals. However, this higher charity percent can be easily explained by a few factors.
1. Trusted, respected individual / group telling people to give - This would be a priest telling people to give to a cause. Since he is a trusted member of a community, the church, and people look up to him, they are more likely to donate. Secular people, missing this community, do not get the same amount of pressure to donate.
2. Peer pressure - You don't want to be the only member of your Church that doesn't give do you?
3.
I'l stop there. The religious part of religion isn't what makes people donate, and thus, the religion itself really has no role to play in it.