Christians, people who lean right, etc tend to give to social welfare organizations like the Salvation Army, Goodwill, foodbanks, etc. Basically groups that help out individuals.

Atheists, people who lean left, etc tend to give to artistic or societal organizations like a symphony, Greenpeace, etc.

I think the reasoning for this is simple. People on the right believe it is up to individuals to solve these problems and don't want the government involved. People on the left believe it is the government's role to solve these problems so they address their interests elsewhere.