Naked Capitalism carried a link to this great little video about Mali's gift economy, called dama. In one of the world's most cash-poor countries, people "pay it forward" with no expectation of something in return. Rather, they recognize their kinship with their fellow humans and trust receivers to give in return to other members of the community.
The next time someone tries to defend Capitalism as a system that reflects a human nature that is selfish and competitive, refer them to this counter-example.